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  • 251.
    Khaji, Zahra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Barbade, Dhananjay
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Palmer, Kristoffer
    SSC Nanospace.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Alumina-based monopropellant microthruster with integrated heater, catalytic bed and temperature sensors2016Conference paper (Refereed)
    Abstract [en]

    A liquid propellant alumina microthruster with an integrated heater, catalytic bed and two temperature sensors has been developed and tested using 30 wt. % hydrogen peroxide. The temperature sensors and the catalytic bed were screen-printed using platinum paste on tapes of alumina that was stacked and laminated before sintering. In order to increase the surface of the catalytic bed, the platinum paste was mixed with a sacrificial paste that disappeared during sintering, leaving behind a porous and rough layer. Complete evaporation and combustion, resulting in only gas coming from the outlet, was achieved with powers above 3.7 W for a propellant flow of 50 μl/min. At this power, the catalytic bed reached a maximum temperature of 147°C. The component was successfully operated up to a temperature of 307°C, where it cracked.

  • 252.
    Khaji, Zahra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Barbade, Dhananjay
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Palmer, Kristoffer
    SSC Nanospace.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Endurance and Failure of an Alumina-based Monopropellant Microthruster with Integrated Heater, Catalytic Bed and Temperature Sensors2017In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 27, no 5, p. 1-11, article id 055011Article in journal (Refereed)
    Abstract [en]

    Monopropellant ceramic microthrusters with an integrated heater, catalytic bed and two temperature sensors, but of various designs, were manufactured by milling a fluidic channel and chamber, and a nozzle, and screen printing platinum patterns on green tapes of alumina that were stacked and laminated before sintering. In order to increase the surface area of the catalytic bed, the platinum paste was mixed with a sacrificial paste that disappeared during sintering, to leave behind a porous and rough layer. As an early development level in manufacturing robust and high-temperature tolerant microthrusters, the influence of design on the temperature gradients and dry temperature tolerance of the devices was studied. On average, the small reaction chambers showed a more than 1.5 times higher dry temperature tolerance (in centigrade) compared to devices with larger chambers, independent of the heater and device size. However, for a given temperature, big devices consumed on average 2.9 times more power than the small ones. It was also found that over the same area and under the same heating conditions, devices with small chambers were subjected to approximately 40% smaller temperature differences. A pressure test done on two small devices with small chambers revealed that pressures of at least 26.3 bar could be tolerated. Above this pressure, the interfaces failed but the devices were not damaged. To investigate the cooling effect of the micropropellant, the endurance of a full thruster was also studied under wet testing where it was fed with 31 wt.% hydrogen peroxide. The thruster demonstrated complete evaporation and/or full decomposition at a power above 3.7 W for a propellant flow of 50 mu l min(-1). At this power, the catalytic bed locally reached a temperature of 147 degrees C. The component was successfully heated to an operating temperature of 307 degrees C, where it cracked. Under these firing conditions, and assuming complete decomposition, calculations give a thrust and specific impulse of 0.96 mN and 106 s, respectively. In the case of evaporation, the corresponding values are calculated to be 0.84 mN and 92 s.

  • 253.
    Khaji, Zahra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Palmer, Kristoffer
    SSC Nanospace, Uppsala, Sweden.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Catalytic Effect of Platinum and Silver in a Hydrogen Peroxide Monopropellant Ceramic MicrothrusterIn: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, ISSN 0924-4247Article in journal (Refereed)
  • 254.
    Khaji, Zahra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Manufacturing and characterization of a ceramic single-use microvalve2016In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 26, no 9, article id 095002Article in journal (Refereed)
    Abstract [en]

    We present the manufacturing and characterization of a ceramic single-use microvalve withthe potential to be integrated in lab-on-a-chip devices, and forsee its utilization in space andother demanding applications. A 3 mm diameter membrane was used as the flow barrier, andthe opening mechanism was based on cracking the membrane by inducing thermal stresses onit with fast and localized resistive heating.

    Four manufacturing schemes based on high-temperature co-fired ceramic technology werestudied. Three designs for the integrated heaters and two thicknesses of 40 and 120 μmfor the membranes were considered, and the heat distribution over their membranes, therequired heating energies, their opening mode, and the flows admitted through were compared.Furthermore, the effect of applying +1 and −1 bar pressure difference on the membraneduring cracking was investigated. Thick membranes demonstrated unpromising results forlow-pressure applications since the heating either resulted in microcracks or cracking of thewhole chip. Because of the higher pressure tolerance of the thick membranes, the designwith microcracks can be considered for high-pressure applications where flow is facilitatedanyway. Thin membranes, on the other hand, showed different opening sizes depending onheater design and, consequently, heat distribution over the membranes, from microcracks toholes with sizes of 3–100% of the membrane area. For all the designs, applying +1 bar overpressure contributed to bigger openings, whereas −1 bar pressure difference only did so forone of the designs, resulting in smaller openings for the other two. The energy required forbreaking these membranes was a few hundred mJ with no significant dependence on designand applied pressure. The maximum sustainable pressure of the valve for the current designand thin membranes was 7 bar.

  • 255.
    Khaji, Zahra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sturesson, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Swedish National Defence College.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Design and fabrication of a miniaturized combustor with integrated oxygen storage and release element2014In: 25th Micromechanics and Microsystems Europe workshop  (MME 2014),2014, P19 (4 pp), 2014Conference paper (Refereed)
    Abstract [en]

    A miniature combustor for converting organic samples into CO2 with application in carbon isotopic measurements of small samples has been manufactured and evaluated. The combustor was made by machining and laminating High-Temperature Co-fired Ceramic (HTCC) 99.99% alumina green tapes and screen printing platinum conductors on them. The device has a built-in heater and a temperature sensor made of platinum, which were co-sintered with the ceramic. A metal oxide (copper oxide) oxygen supply was added to the combustor after sintering by in-situ electroplating of copper on the heater pattern followed by thermal oxidation. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Thermal Gravimetric Analysis (TGA) were used to study electroplating, oxidation and the oxide decompo-sition processes.

  • 256.
    Khaji, Zahra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sturesson, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC). Swedish National Defence College.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Investigation of the storage and release of oxygen in a Cu-Pt element of a high-temperature microcombustor2014In: The 14th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications(PowerMEMS 2014), Institute of Physics (IOP), 2014Conference paper (Refereed)
    Abstract [en]

    A miniature combustor for converting organic samples into CO2 with application in carbon isotopic measurements has been manufactured and evaluated. The combustor was made of High-Temperature Co-fired Ceramic (HTCC) alumina green tapes. The device has a built-in screen printed heater and a temperature sensor made of platinum, co-sintered with the ceramic. A copper oxide oxygen supply was added to the combustor after sintering by in-situ electroplating of copper on the heater pattern followed by thermal oxidation. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Thermal Gravimetric Analysis (TGA) were used to study electroplating, oxidation and the oxide reduction processes. The temperature sensor was calibrated by use of a thermocouple. It demonstrates a temperature coefficient resistance of 4.66×10−3/°C between 32 and 660 °C. The heat characterization was done up to 1000 °C by using IR thermography, and the results were compared with the data from the temperature sensor. Combustion of starch confirmed the feasibility of using copper oxide as the source of oxygen of combustion.

  • 257.
    Khaji, Zahra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sturesson, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Swedish National Defence College.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Manufacturing and characterization of a ceramic microcombustor with integrated oxygen storage and release element2015In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 25, no 10, article id 104006Article in journal (Refereed)
    Abstract [en]

    A microscale ceramic high-temperature combustor with a built-in temperature sensor and source of oxygen has been designed, manufactured and characterized. The successful in situ electroplating and oxidation of copper, and the use of copper oxide as the source of oxygen were demonstrated. It was shown that residual stresses from electroplating, copper oxidation and oxide decomposition did not cause much deformation of the substrate but influenced mainly the integrity and adhesion of the metal films. The process had influence on the electrical resistances, however. Calibration of the temperature sensor and correlation with IR thermography up to 1000°C revealed a nearly linear sensor behavior. Demonstration of combustion in a vacuum chamber proved that no combustion had occurred before release of oxygen from the metal oxide resource.

  • 258.
    Khaji, Zhara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sturesson, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Extending Microsensor Technology to Very High Temperatures2014Conference paper (Other academic)
  • 259.
    Kim, Anna A
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Stanford University, University of California Santa Barbara.
    Montell, Denise
    University of California Santa Barbara.
    Pruitt, Beth
    University of California Santa Barbara.
    O'Brien, Lucy
    Stanford University.
    Regional Calcium Dynamics in Drosophila Adult Midgut2019In: Mol. Biol. Cell, 2019, Vol. 28, article id P2637Conference paper (Other academic)
    Abstract [en]

    Although calcium dynamics are widely studied in cell culture, little has been reported on the topic for adult organs. We find striking regional and cell-type specific differences in calcium dynamics in the three major cell types of the adult Drosophila intestine. 

    The adult fruit fly intestine is a compelling platform for studying intercellular dynamics and interactions. This stem cell-based epithelium is a reductionist model system of the mammalian small bowel with conserved features. The multi-cellular epithelium consists of three major cell types: progenitor cells that give rise to new cells (including stem cells), enteroendocrine cells that are hormone signaling cells, and enterocytes that are large absorptive cells.

    We find regional and cell-type specific variations in calcium signaling dynamics within this functionally compartmentalized organ, using confocal imaging of ex vivo cultured fly intestines. Progenitor and enteroendocrine cells indicate oscillatory intracellular calcium dynamics of slower and faster frequencies respectively, and enterocytes demonstrate the presence of traveling calcium waves. Our findings may establish a novel model for studying spatio-temporal organization of cellular to organ-level calcium dynamics in a renewable adult organ.

  • 260.
    Kim, Anna A
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Stanford University, USA; University of California, Santa Barbara, USA.
    Nekimken, Adam L
    Stanford University, USA.
    Fechner, Sylvia
    Stanford University, USA.
    O'Brien, Lucy E
    Stanford University, USA.
    Pruitt, Beth L
    University of California, Santa Barbara, USA; Stanford University, USA.
    Microfluidics for mechanobiology of model organisms2018In: Microfluidics in Cell Biology Part A: Microfluidics for Multicellular Systems, Elsevier, 2018, Vol. 146, p. 217-259, article id S0091-679X(18)30063-3Chapter in book (Refereed)
    Abstract [en]

    Mechanical stimuli play a critical role in organ development, tissue homeostasis, and disease. Understanding how mechanical signals are processed in multicellular model systems is critical for connecting cellular processes to tissue- and organism-level responses. However, progress in the field that studies these phenomena, mechanobiology, has been limited by lack of appropriate experimental techniques for applying repeatable mechanical stimuli to intact organs and model organisms. Microfluidic platforms, a subgroup of microsystems that use liquid flow for manipulation of objects, are a promising tool for studying mechanobiology of small model organisms due to their size scale and ease of customization. In this work, we describe design considerations involved in developing a microfluidic device for studying mechanobiology. Then, focusing on worms, fruit flies, and zebrafish, we review current microfluidic platforms for mechanobiology of multicellular model organisms and their tissues and highlight research opportunities in this developing field.

  • 261.
    Klintberg, Lena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Som man frågar får man svar: studenter formulerar frågor och väljer lärstrategi2015In: 5:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar, Uppsala, 2015Conference paper (Refereed)
    Abstract [sv]

    Blooms taxonomi kategoriserar olika lärstrategierefter komplexitetsgrad. Nybörjare är faktafokuserade eftersomdet är mer krävande att analysera, bedöma och värderakunskaper. Valet av lärstrategi är situationsberoende ochfaktorer som motivation och nyfikenhet leder ofta till ett merkomplext angreppssätt. För att undersöka vad civilingenjörsstudentersom läser näst sista året själva spontant väljerför lärstrategier, fick 43 studenter läsa in ett antal artiklar somett moment i kursen Mikro- och nanoteknik I. Därefter ombadsde formulera frågor på materialet. I ett försök att aktivt påverkade lärstrategier som studenterna valde skulle frågorna bådeberöra sådant studenterna identifierade som värdefull kunskapsamt sådant artiklarna inte gav svar på men som de skulle viljaveta. Studenterna fick sedan klassificera frågorna enligt Bloomstaxonomi. För ett antal utvalda frågor jämfördes därefterklassificeringen med en som lärarkollegiet gjorde och resultatetblev att lärarna tenderade att ranka de enkla frågorna högre ochmer komplicerade frågor lägre jämfört med studenterna. I en uppföljningsstudie undersöktes om studenterna ansåg attuppgiften att själv få formulera frågor gett dem bättreförståelsen och fått dem att fundera mer över materialet jämfört med om de fått instuderingsuppgifter. Resultatet visar att praktiskt taget alla studenter spontantställt minst en fråga som de kategoriserat ibland de högsta komplexitetsnivåerna och som tillsammans täcker de inkomna frågorna de aspekter som lärarkollegiet anser är viktigt imaterialet. Vissa artiklar visade sig stimulera till frågor med högre komplexitet och det fanns ett tydligt samband som visadeatt mer komplexa frågor ställdes då svaren inte fanns imaterialet. Hela 68% av studenterna bedömde att metoden att själva få formulera frågor på materialet givit dem en bättre förståelse jämfört med om de fått färdiga frågor att besvara efter inläsningen. Frågorna visade sig också ge värdefull insikt i vad studenterna funderar på och är nyfikna att veta mer om, t ex aspekter rörande miljö, hälsa och ekonomi.

  • 262.
    Klintberg, Lena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Viberg, Pernilla
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Förmedling av komplexa begrepp i multidisciplinär kurs på avancerad niv2013Conference paper (Refereed)
    Abstract [sv]

    Vid undervisning på avancerad nivå i en multidisciplinär kurs används och behandlas vanligtvis komplexa begrepp från flera olika ämnesområden. Vid samläsning över olika program, skiljer sig studenternas förkunskaper åt även om studenterna från de olika programmen formellt uppfyller förkunskapskraven. Detta inverkar på studenternas förmåga att tillgodogöra sig kursens innehåll.

    En studie har gjorts på en kurs i mikro- och nanoteknik, som ges under 4:e året på flera olika civilingenjörsprogram. Med anledning av de identifierade skillnaderna, har en undersökning av tidigare studenters erfarenhet av kursen gjorts. Dessutom har de blivande studenternas förkunskaper inventerats och jämförts med de begrepp som används i kursen.

    Resultatet visar att studenterna i kemiteknik i viss utsträckning förfördelats även om skillnaderna är små.

    16% av studenterna som läst teknisk fysik med material­vetenskap (MV) når högsta betyg på kursen jämfört med 10% för studenterna i kemiteknik (KT), men i medelbetyg är det ingen signifikant skillnad mellan studentgrupperna. Vid rankning av påståendet ”Nya begrepp introducerades på ett bra och tydligt sätt” gav MV-studenterna 4,0 i medel medan KT studenterna gav 3,5 på skalan 1 (aldrig) till 5 (alltid). Syftet med denna undersökning är att, utifrån de identifierade skillnaderna, kunna hitta nya sätt att introducera och exemplifiera begreppen så att studentgrupperna får likvärdiga förutsättningar att tillgodogöra sig kursens innehåll.

  • 263.
    Knaust, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Microsystems for Harsh Environments2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    When operating microsystems in harsh environments, many conventionally used techniques are limiting. Further, depending on if the demands arise from the environment or the conditions inside the system, different approaches have to be used. This thesis deals with the challenges encountered when microsystems are used at high pressures and high temperatures.

    For microsystems operating at harsh conditions, many parameters will vary extensively with both temperature and pressure, and to maintain control, these variations needs to be well understood. Covered within this thesis is the to-date strongest membrane micropump, demonstrated to pump against back-pressures up to 13 MPa, and a gas-tight high pressure valve that manages pressures beyond 20 MPa.

    With the ability to manipulate fluids at high pressures in microsystems at elevated temperatures, opportunities are created to use green solvents like supercritical fluids like CO2. To allow for a reliable and predictable operation in systems using more than one fluid, the behavior of the multiphase flow needs to be controlled. Therefore, the effect of varying temperature and pressure, as well as flow conditions were investigated for multiphase flows of CO2 and H2O around and above the critical point of CO2. Also, the influence of channel surface and geometry was investigated.

    Although supercritical CO2 only requires moderate temperatures, other supercritical fluids or reactions require much higher temperatures. The study how increasing temperature affects a system, a high-temperature testbed inside an electron microscope was created.

    One of the challenges for high-temperature systems is the interface towards room temperature components. To circumvent the need of wires, high temperature wireless systems were studied together with a wireless pressure sensing system operating at temperatures up to 1,000 °C for pressures up to 0.3 MPa.

    To further extend the capabilities of microsystems and combine high temperatures and high pressures, it is necessary to consider that the requirements differs fundamentally. Therefore, combining high pressures and high temperatures in microsystems results in great challenges, which requires trade-offs and compromises. Here, steel and HTCC based microsystems may prove interesting alternatives for future high performance microsystems.

    List of papers
    1. High-Pressure Peristaltic Membrane Micropump With Temperature Control
    Open this publication in new window or tab >>High-Pressure Peristaltic Membrane Micropump With Temperature Control
    Show others...
    2010 (English)In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 19, no 6, p. 1462-1469Article in journal (Refereed) Published
    Abstract [en]

    A high-pressure peristaltic membrane micropump, which is capable of pumping against a back pressure of 150 bar, has been evaluated. The main focus was to maintain the flow characteristics also at high back pressures. The pump was manufactured by fusion bonding of parylene-coated stainless-steel stencils. A large-volume expansion connected to the solid-to-liquid phase transition in paraffin was used to move 10 µm stainless-steel membranes. The pump was evaluated by using two different driving schemes, a four-phase cycle and a six-phase cycle. With the six-phase cycle, a constant flow rate of 0.4 µL min-1 was achieved over an interval ranging from atmospheric pressure to 130 bar. At lower back pressures, the more energy efficient four-phase cycle achieved slightly higher flow rates than the six-phase cycle. However, it required higher driving voltage at high back pressures. Since the pump is thermally activated, a temperature sensor was integrated to control the melting and solidification of paraffin, implying capability of increasing the performance of the pump. With a thickness of only 1 mm as well as a simple and robust design, the micropump is well suited for integration in analytical systems. The high pressures managed are in the region needed for, e.g., high-performance liquid chromatography systems.

    Keywords
    High back pressure, integrated temperature sensor, paraffin actuator, peristaltic micropump, pressure-independent flow, stainless-steel membrane
    National Category
    Materials Engineering
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-139213 (URN)10.1109/JMEMS.2010.2076784 (DOI)000284875400020 ()
    Available from: 2010-12-22 Created: 2010-12-22 Last updated: 2017-12-11Bibliographically approved
    2. High-pressure stainless steel active membrane microvalves
    Open this publication in new window or tab >>High-pressure stainless steel active membrane microvalves
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    2011 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 21, no 7, p. 075010-Article in journal (Refereed) Published
    Abstract [en]

    In this work, high-pressure membrane microvalves have been designed, manufactured andevaluated. The valves were able to withstand back-pressures of 200 bar with a response timeof less than 0.6 s. These stainless steel valves, manufactured with back-end batch production,utilize the large volume expansion coupled to the solid–liquid phase transition in paraffin wax.When membrane materials were evaluated, parylene coated stainless steel was found to be thebest choice as compared to polydimethylsiloxane and polyimide. Also, the influence of theorifice placement and diameter is included in this work. If the orifice is placed too close to therim of the membrane, the valve can stay sealed even after turning the power off, and the valvewill not open until the pressure in the system is released. The developed steel valves, evaluatedfor both water and air, provide excellent properties in terms of mechanical stability, ease offabrication, and low cost. Possible applications include sampling at high pressures, chemicalmicroreactors, high performance liquid chromatography, pneumatics, and hydraulics.

    Keywords
    stainless steel, high pressure microvalve, paraffin
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-131007 (URN)10.1088/0960-1317/21/7/075010 (DOI)000291935000024 ()
    Available from: 2010-09-20 Created: 2010-09-20 Last updated: 2017-12-12Bibliographically approved
    3. On-chip pump system for high-pressure microfluidic applications
    Open this publication in new window or tab >>On-chip pump system for high-pressure microfluidic applications
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    2013 (English)Conference paper, Poster (with or without abstract) (Refereed)
    Abstract [en]

    This paper presents a micropump system with four integrated paraffin actuated pumps: Two mobile phase pumps and two sample injector pumps. The mobile phase pumps are evaluated by their ability to deliver a stable, low-ripple flow to be used in chip-based high performance liquid chromatography. It is shown that the two mobile phase pumps can be driven in combined operation with an induced offset to significantly lower flow fluctuations.

    Keywords
    High Pressure, Paraffin, Phase Change Material, Microelectromechanical Systems
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-204725 (URN)
    Conference
    µTAS 2013
    Funder
    Swedish Research Council
    Available from: 2013-08-09 Created: 2013-08-09 Last updated: 2015-09-07
    4. Influence of flow rate, temperature and pressure on multiphase flows of supercritical carbon dioxide and water using multivariate partial least square regression
    Open this publication in new window or tab >>Influence of flow rate, temperature and pressure on multiphase flows of supercritical carbon dioxide and water using multivariate partial least square regression
    Show others...
    2015 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 25, no 10, article id 105001Article in journal (Refereed) Published
    Abstract [en]

    Supercritical carbon dioxide (scCO2) is often used to replace harmful solvents and can dissolve a wide range of organic compounds. With a favorable critical point at 31 °C and 7.4 MPa, reaching above the critical point for scCO2 is fairly accessible. Because of the compressible nature of scCO2 and the large changes of viscosity and density with temperature and pressure, there is a need to determine the behavior of scCO2 in microfluidic systems. Here, the influence of how parameters such as flow rate, temperature, pressure, and flow ratio affects the length of parallel flow of water and scCO2 and the length of the created CO2 segments are investigated and modeled using multivariate data analysis for a 10 mm long double-y channel. The parallel length and segment size were observed in the laminar regime around and above the critical point of CO2. The flow ratio between the two fluids together with the flow rate influenced both the parallel length and the segment sizes, and a higher pressure resulted in shorter parallel lengths. Regarding the segment length of CO2, longer segments were a result of a higher Weber number for H2O together with a higher temperature in the channel. 

    Keywords
    Supercritical fluids, microfluidics, carbon dioxide, partial least square regression, principal component analysis, fluid dynamics, multiphase flow
    National Category
    Engineering and Technology Other Materials Engineering
    Identifiers
    urn:nbn:se:uu:diva-253552 (URN)10.1088/0960-1317/25/10/105001 (DOI)000366827400017 ()
    Funder
    Swedish Research Council, 2011-5037Knut and Alice Wallenberg Foundation
    Available from: 2015-05-29 Created: 2015-05-29 Last updated: 2018-06-19Bibliographically approved
    5. Influence of surface modifications and channel structure for microflows of supercritical carbon dioxide and water
    Open this publication in new window or tab >>Influence of surface modifications and channel structure for microflows of supercritical carbon dioxide and water
    2016 (English)In: Journal of Supercritical Fluids, ISSN 0896-8446, E-ISSN 1872-8162, Vol. 107, p. 649-656Article in journal (Refereed) Published
    Abstract [en]

    Miniaturization offers a possibility to increase the performance and decrease the time scales of systems. Existing microsystems using supercritical CO2 mainly utilizes multiphase segmented flows. To allow for a broader toolbox for future systems, also parallel flows are useful which eases the separation of the different phases. Here, the effect of different surface coatings are studied for multiphase flows of scCO2 and H2O in flat microchannels, with and without a 4 μm high ridge guide, which allows for pinning of the fluid interface inside the 190 μm wide and 35 μm high channel. Three different surfaces with different wettings towards scCO2 and H2O are studied, where a surface terminated with a hydrocarbon-based silane was observed to be neutral in the H2O/scCO2 system, a surface terminated with a fluorocarbon-based silane was hydrophobic, and an uncoated glass surface was hydrophilic.

    Using two flow rates of 5:5 μl/min (CO2:H2O) and 6.5:3.5 μl/min (CO2:H2O), a parallel flow between scCO2 and H2O was observed for uncoated and flat channels where the H2O flow pushed the CO2 to the side, before the flows eventually breaks up into segments. With a ridge guide in the middle of the channel, the interface was pinned at half the channel width, although still breaking up into segments. The neutral hydrocarbon-based surface coating with approximately 90° contact angles resulted in evenly created segments without a ridge guide. Including a guide in the middle of the channel, a parallel flow was observed throughout the channel, although occasionally small CO2 segments entered the H2O outlet. Using the fluorocarbon-based silane resulted in an unstable segmented system with pressure fluctuations.

    Using surface modifications, an increased control can be achieved for either segmentation or parallel flow where a neutral surface is favored for a stable flow behavior. Together with a ridge guide, the fluid interface was pinned at the center. 

    Keywords
    Microfluidics, Supercritical CO2, Silane coating, Parallel flow, Segmented flow, Surface modification
    National Category
    Engineering and Technology Chemical Engineering
    Identifiers
    urn:nbn:se:uu:diva-253554 (URN)10.1016/j.supflu.2015.07.027 (DOI)000366077100077 ()
    Funder
    Swedish Research Council, 2011-5037Knut and Alice Wallenberg Foundation
    Available from: 2015-05-29 Created: 2015-05-29 Last updated: 2018-06-19Bibliographically approved
    6. Characterization of dielectric properties of polycrystalline aluminum nitride for high temperature wireless sensor nodes
    Open this publication in new window or tab >>Characterization of dielectric properties of polycrystalline aluminum nitride for high temperature wireless sensor nodes
    2013 (English)In: 13th International Conference on Micro And Nanotechnology for Power Generation and Energy Conversion Applications (Powermems 2013), 2013Conference paper, Published paper (Refereed)
    Abstract [en]

    An aluminium nitride (AIN) passive resonance circuit intended for thermally matched high temperature wireless sensor nodes (WSN) was manufactured using thick-film technology. Characterization was done for temperatures up to 900 C in both a hot-chuck for frequencies below 5 MHz, and using wireless readings of resonating circuits at 15 MHz, 59 MHz, and 116 MHz. The substrate for the circuits was sintered polycrystalline AIN. Using a simplified model for the resonators where the main contribution of the frequency-shift was considered to come from a shift of the dielectric constant for these frequencies, the temperature dependency of the dielectric constant for AIN was found to decrease with increasing frequency up to 15 MHz. With an observed frequency shift of 0.04% at 15 MHz, and up to 0.56% at 59 MHz over a temperature range of 900 C, AIN looks as a promising material for integration of resonance circuits directly on the substrate.

    Series
    Journal of Physics Conference Series, ISSN 1742-6588 ; 476
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-218528 (URN)10.1088/1742-6596/476/1/012101 (DOI)000329347500100 ()
    Conference
    13th International Conference on Micro- and Nano-Technology for Power Generation and Energy Conversion Applications (PowerMEMS), DEC 03-06, 2013, London, ENGLAND
    Available from: 2014-02-13 Created: 2014-02-12 Last updated: 2015-09-07Bibliographically approved
    7. Thermomechanical properties and performance of ceramic resonators for wireless pressure reading in high temperatures
    Open this publication in new window or tab >>Thermomechanical properties and performance of ceramic resonators for wireless pressure reading in high temperatures
    Show others...
    2015 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 25, no 9, article id 095016Article in journal (Refereed) Published
    Abstract [en]

    This paper reports on the design, fabrication and thermomechanical study of ceramic LC resonators for wireless pressure reading, verified at room temperature, at 500 °C and at 1000 °C for pressures up to 2.5 bar. Five different devices were fabricated of high-temperature co-fired ceramics (HTCC) and characterized. Alumina green tape sheets were screen printed with platinum paste, micromachined, laminated and fired. The resulting samples were 21 x 19 mm2 with different thicknesses. An embedded communicator part was integrated with either a passive backing part or with a pressure-sensing element, including an 80 μm thick and 6 mm diameter diaphragm. The study includes measuring thermally and mechanically induced resonance frequency shifts, and thermally induced deformations. For the pressure sensor device, contributions from changes in the relative permittivity and from expanding air, trapped in the cavity, were extracted. The devices exhibited thermomechanical robustness during heating, regardless of the thickness of the backing. The pressure sensitivity decreased with increasing temperature from 15 050 ppm/bar at room temperature to 2400 ppm/bar at 1000°C, due to the decreasing pressure difference between the external pressure and the air pressure inside the cavity. 

    Keywords
    Wireless Reading, HTCC, Pressure sensing, Harsh Environments, Thermomechanical properties
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-253555 (URN)10.1088/0960-1317/25/9/095016 (DOI)000365167700023 ()
    Funder
    Knut and Alice Wallenberg Foundation
    Available from: 2015-05-29 Created: 2015-05-29 Last updated: 2018-08-03Bibliographically approved
    8. ESEM as a Tool for Studying High Temperature Electronics
    Open this publication in new window or tab >>ESEM as a Tool for Studying High Temperature Electronics
    2011 (English)In: IMAPS High Temperature Electronics Network (HiTEN 2011), July 18-20, 2011 ,Oxford, UK, 2011Conference paper, Published paper (Refereed)
    Abstract [en]

    Researchers studying materials and processes at high temperatures are often restricted to do evaluation afterwards and at room temperature using e.g. scanning electron microscopy (SEM). Limited by high vacuum, outgassing and non-conducting samples are difficult to study with SEM. For such samples, environmental scanning electron microscope (ESEM) is an alternative that is particularly suited also for high temperature in-situ studies. The electron detector in the ESEM make use of otherwise unwanted scattering of electrons as an amplifier of the signal, and by using differential pumping, it is possible to introduce several mbar of either oxygen, water vapor, or a gas of choice into the sample chamber while still maintaining the high-vacuum in the electron column. The auxiliary gas neutralizes surface charges built up by the electron beam, which makes it possible to image non-conductive and outgassing samples, thus making it possible to study e.g. polymeric and high temperature materials. Our ESEM, FEI XL30, have a heating stage making it possible to reach temperatures up to 1500°C. Equipped with electrical feed- throughs, the instrument can be used to study high temperature phenomena on electrically activated components.

    ESEM is an instrument that has found its use for biological and organic samples. However, less work has been done using it for high temperature processes. Here, we show real-time imaging of the sintering of dielectric and Ag thick-film prints on AlN substrates. The use of the electrical feed-throughs to activate electrical components and study them at high temperatures is also demonstrated. ESEM is a versatile tool for high temperature studies and in-situ analysis of electrical components, solder processes and different die-attach materials. 

    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-159036 (URN)
    Conference
    HiTEN 2011
    Projects
    wisenet
    Available from: 2011-09-21 Created: 2011-09-21 Last updated: 2016-04-20
  • 264.
    Knaust, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Andersson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Influence of surface modifications and channel structure for microflows of supercritical carbon dioxide and water2016In: Journal of Supercritical Fluids, ISSN 0896-8446, E-ISSN 1872-8162, Vol. 107, p. 649-656Article in journal (Refereed)
    Abstract [en]

    Miniaturization offers a possibility to increase the performance and decrease the time scales of systems. Existing microsystems using supercritical CO2 mainly utilizes multiphase segmented flows. To allow for a broader toolbox for future systems, also parallel flows are useful which eases the separation of the different phases. Here, the effect of different surface coatings are studied for multiphase flows of scCO2 and H2O in flat microchannels, with and without a 4 μm high ridge guide, which allows for pinning of the fluid interface inside the 190 μm wide and 35 μm high channel. Three different surfaces with different wettings towards scCO2 and H2O are studied, where a surface terminated with a hydrocarbon-based silane was observed to be neutral in the H2O/scCO2 system, a surface terminated with a fluorocarbon-based silane was hydrophobic, and an uncoated glass surface was hydrophilic.

    Using two flow rates of 5:5 μl/min (CO2:H2O) and 6.5:3.5 μl/min (CO2:H2O), a parallel flow between scCO2 and H2O was observed for uncoated and flat channels where the H2O flow pushed the CO2 to the side, before the flows eventually breaks up into segments. With a ridge guide in the middle of the channel, the interface was pinned at half the channel width, although still breaking up into segments. The neutral hydrocarbon-based surface coating with approximately 90° contact angles resulted in evenly created segments without a ridge guide. Including a guide in the middle of the channel, a parallel flow was observed throughout the channel, although occasionally small CO2 segments entered the H2O outlet. Using the fluorocarbon-based silane resulted in an unstable segmented system with pressure fluctuations.

    Using surface modifications, an increased control can be achieved for either segmentation or parallel flow where a neutral surface is favored for a stable flow behavior. Together with a ridge guide, the fluid interface was pinned at the center. 

  • 265.
    Knaust, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Andersson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Mannitol for High Temperature Phase Change Actuators2014Conference paper (Other academic)
    Abstract [en]

    To enable valves for hot water microsystems, the possibility of using the volume expansion of the phase transition from solid to liquid in mannitol for strong high temperature actuators was studied. From room temperature to 160°C, a linear expansion of 4% was measured, and the expansion at the phase transition from solid to liquid at 160°C to 180°C was measured to be 7%. Stainless steel structures with a stainless steel diaphragm was filled and repeatedly heated up to 180◦C while measuring the deflection of the diaphragm using a laser sensor. The height differences was measured to be 25 μm at 180°C.

    In combination with a fluidic system, the mannitol actuator should capable as a valve for hot water microsystems. 

  • 266.
    Knaust, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Andersson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Rogeman, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Amberg, Gustav
    KTH.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Influence of flow rate, temperature and pressure on multiphase flows of supercritical carbon dioxide and water using multivariate partial least square regression2015In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 25, no 10, article id 105001Article in journal (Refereed)
    Abstract [en]

    Supercritical carbon dioxide (scCO2) is often used to replace harmful solvents and can dissolve a wide range of organic compounds. With a favorable critical point at 31 °C and 7.4 MPa, reaching above the critical point for scCO2 is fairly accessible. Because of the compressible nature of scCO2 and the large changes of viscosity and density with temperature and pressure, there is a need to determine the behavior of scCO2 in microfluidic systems. Here, the influence of how parameters such as flow rate, temperature, pressure, and flow ratio affects the length of parallel flow of water and scCO2 and the length of the created CO2 segments are investigated and modeled using multivariate data analysis for a 10 mm long double-y channel. The parallel length and segment size were observed in the laminar regime around and above the critical point of CO2. The flow ratio between the two fluids together with the flow rate influenced both the parallel length and the segment sizes, and a higher pressure resulted in shorter parallel lengths. Regarding the segment length of CO2, longer segments were a result of a higher Weber number for H2O together with a higher temperature in the channel. 

  • 267.
    Knaust, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Khaji, Zahra
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sturesson, P.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Characterization of dielectric properties of polycrystalline aluminum nitride for high temperature wireless sensor nodes2013In: 13th International Conference on Micro And Nanotechnology for Power Generation and Energy Conversion Applications (Powermems 2013), 2013Conference paper (Refereed)
    Abstract [en]

    An aluminium nitride (AIN) passive resonance circuit intended for thermally matched high temperature wireless sensor nodes (WSN) was manufactured using thick-film technology. Characterization was done for temperatures up to 900 C in both a hot-chuck for frequencies below 5 MHz, and using wireless readings of resonating circuits at 15 MHz, 59 MHz, and 116 MHz. The substrate for the circuits was sintered polycrystalline AIN. Using a simplified model for the resonators where the main contribution of the frequency-shift was considered to come from a shift of the dielectric constant for these frequencies, the temperature dependency of the dielectric constant for AIN was found to decrease with increasing frequency up to 15 MHz. With an observed frequency shift of 0.04% at 15 MHz, and up to 0.56% at 59 MHz over a temperature range of 900 C, AIN looks as a promising material for integration of resonance circuits directly on the substrate.

  • 268. Kolari, K.
    et al.
    Havia, T.
    Stuns, I.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Flow restrictor silicon membrane microvalve actuated by optically controlled paraffin phase transition2014In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 24, no 8, p. 084003-Article in journal (Refereed)
    Abstract [en]

    Restrictor valves allow proportional control of fluid flow but are rarely integrated in microfluidic systems. In this study, an optically actuated silicon membrane restrictor microvalve is demonstrated. Its actuation is based on the phase transition of paraffin, using a paraffin wax mixed with a suitable concentration of optically absorbing nanographite particles. Backing up the membrane with oil (the melted paraffin) allows for a compliant yet strong contact to the valve seat, which enables handling of high pressures. At flow rates up to 30 mu L min(-1) and at a pressure of 2 bars, the valve can successfully be closed and control the flow level by restriction. The use of this paraffin composite as an adhesive layer sandwiched between the silicon valve and glass eases fabrication. This type of restrictor valve is best suited for high pressure, low volume flow silicon-based nanofluidic systems.

  • 269. Kolari, Kai
    et al.
    Havia, T
    Stuns, Ingvar
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Optically driven microfluidic flow controller based on thermal expansion2013In: 24th Micromachine Europe, 2013, p. P35-Conference paper (Other academic)
  • 270. Kolari, Kai
    et al.
    Mojzita, D
    Stuns, Ingvar
    Pentillä, M
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Study of population dynamics of E. Coli in a microfluidic landscape incorporating a toxic gradient2013In: 23rd Micromachine Europe (MME 2012, Sept. 9-12, 2013, Ilmenau, Germany), 2013, p. D11-Conference paper (Other academic)
  • 271.
    Kratz, Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Karlsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Köhler, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Analysis of Thermal Transients in an Asymmetric Silicon-Based Heat Dissipation Stage2007In: IEEE transactions on components and packaging technologies (Print), ISSN 1521-3331, E-ISSN 1557-9972, Vol. 30, no 3, p. 444-456Article in journal (Refereed)
    Abstract [en]

    Thermal management is crucial for many microsystems and electronics applications (and that of miniaturized spacecraft is particularly demanding). This paper presents thermal modeling and scaling of a generic multiwafer silicon segment for placement in between two devices, or as a stage for a single one, in need of asymmetric thermal management. The unit is autonomous, i.e., it doesn't require any input signals or power. It comprises paraffin acting both as a heat sink, or thermal storage, and a material activating heat switches. The former mitigates heat bursts and accommodates power initially generated in, e.g., attached electronics, whereas the latter facilitates heat dissipation through heat guides during more intensive operation. Its function and physical properties are described in detail. A lumped thermal model has been constructed and implemented in the Simulink environment to investigate effects from: physical scaling of the unit, and change of its boundary temperature and coupling thereto, power generated, its emission and absorption properties and area fractions dedicated for passive devices, infrared (IR) emission, and heat guides on the unit's exterior, as well as fractional cross sections of paraffin, heat guides and other structural material in its interior. Conclusions, based on simulation results, are made and design rules based on the thermal modeling are presented. It was found that a 68 times 68 mm module could handle more than 10 W for 6 min in its heat sink mode alone. Subjected to 15 W for the same time, the module enters its active dissipation mode by closing its heat switches. A lateral increase and simultaneous vertical decrease of the unit's size resulted in overheating, whereas most scaling did not cause depletion of the heat sink. Changing the area fractions of various constituents also indicated operational stability with exception for excessive enlargement of passive heat guide material, exchanging structural material with paraffin, - or severely limiting IR emission (by emitter area reduction or using low emission material), or using high absorbance material. Altering the boundary temperature and interface conductance proved to be means of biasing the system to various operating temperatures.

  • 272.
    Kratz, Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Eriksson, Anders
    Karlsson, Mikael
    Köhler, Johan
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Dynamic Simulation of an Asymmetric Thermal Management Segment for Multilayered Silicon Microsystems2006In: IEEE Transactions on Components and Packaging TechnologiesArticle in journal (Refereed)
  • 273.
    Kratz, Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Karlsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Köhler, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Stenmark, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Design and Modeling of a thermally regulated communications module for nanospacecraft2006In: Journal of Spacecraft and Rockets, ISSN 0022-4650, E-ISSN 1533-6794, Vol. 43, no 6, p. 1377-1386Article in journal (Refereed)
    Abstract [en]

    A silicon-based integrated communications and thermal management microsystem qualifying for use on Nanospace-1, a modularized microsystem-based advanced integrated nanospacecraft, is presented. The transmitter and receiver share the same module framework with essential differences only in the electronics implementation. A data rate of 1 Mbps for the transmitter and 114 kbps for the receiver is accomplished with a transmitter power for the spacecraft and ground station of 2 and 10 W, respectively. Concurrent triple usage of paraffin as low loss antenna substrate, actuator material, and heat sink is designed and analyzed for the first time. On low-power or short-time high-power dissipation of heat from the electronics, energy is stored as latent heat in this phase-change material acting as a heat sink. Thermal transport through the module is initiated,by actuation of thermal switches when 75% of the paraffin's latent heat is consumed. A static thermal analysis reveals a thermal modulation factor of 5.6 between the on and off states of the thermal switches. The size of the module is 6.6 x 68 x 68 mm, and its weight is 43 g.

  • 274.
    Kratz, Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Köhler, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Stenmark, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Nanospacecraft technology and its predicted consequences for the space community2006In: IEEE Transactions on Aerospace and Electronic SystemsArticle in journal (Refereed)
  • 275.
    Kratz, Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Öjefors, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Stenmark, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Micromachined S-band Patch Antenna with Reduced Dielectric Constant2006In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 130-131, p. 478-484Article in journal (Refereed)
    Abstract [en]

    A generic dielectric constant reduction method for silicon substrates is presented in detail along with a process description to produce variable dielectric layers for planar antennas. Virtually any dielectric constant below the value for solid silicon 11.9 can be produced down to the limit of structural durability. A first-order volumetric average yields a dielectric constant of 3.8 for the following bonded micromachined silicon substrates; small honeycomb cells with wall thickness of 16 μm and inner wall length of 87 μm are etched using deep reactive ion etch (DRIE) to 475 μm depth in each of two 525 μm 4 in. high ohmic wafers. These two wafers are bonded together with the etched side of both wafers facing each other. A manufactured coaxial-fed disk-patch S-band antenna illustrates the method to reduce the dielectric constant for a circular zone with a diameter of 50 mm. The antenna is designed for a center frequency of 2.5 GHz based on a lossless substrate with a dielectric constant of 3.8. Adjusting the simulation model to fit the measured values of the antenna indicates a dielectric constant of 2.2, a dielectric loss tangent of 0.002, a bulk conductivity loss of 0.006 S/m, and a resonance frequency of 3.2 GHz. A low frequency analysis in the interval 200–500 MHz with a lumped element model and a low frequency formula for the capacitance between the patch and ground plane indicates a dielectric constant in the order of 2.7–2.8. Based on measurements in an SEM, a corrected average dielectric constant is found to be 2.9. This correction is due to thinner walls than expected in the manufactured honeycomb structure. Antenna lobe characteristics have been measured with a half-power beamwidth of ∼76° in both the E-plane and H-plane at 3.2 GHz.

  • 276.
    Kratz, Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Öjefors, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Thorslund, Robert
    Köhler, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signal Processing.
    Stenmark, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Micromachined Ka-band Microsystem for Agile High Speed Telemetry2006In: International Journal of Satellite Communications and NetworkingArticle in journal (Refereed)
  • 277.
    Köhler, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Bejhed, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Kratz, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Bruhn, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Lindberg, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Stenmark, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    A Hybrid Cold Gas Microthruster System for Spacecraft2002In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 97-98, p. 587-98Article in journal (Refereed)
    Abstract [en]

    A hybrid cold gas microthruster system suitable for low Δv applications on spacecraft have been developed. Microelectromechanical system (MEMS) components together with fine-mechanics form the microthruster units, intergrating four independent thrusters. These are designed to deliver maximum thrusts in the range of 0.1–10 mN.

    The system includes three different micromachined subsystems: a nozzle unit comprising four nozzles generating supersonic gas velocity, i.e. 455 m/s, four independent piezoelectric proportional valves with leak rates at 10−6 scc/s He, and two particle filters. The performances of all these MEMS subsystems have been evaluated.

    The total system performance has been estimated in two parameters, the system-specific impulse and the mass ratio of the propulsion system to the spacecraft mass. These figures provide input for spacecraft design and manufacture.

  • 278. Köhler, Johan
    et al.
    Kratz, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Nguyen, Hugo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Modular Multifunctional Silicon Microsystems for Spacecraft Applications2007Conference paper (Refereed)
  • 279.
    Lansåker, Pia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Roos, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Au-based transparent conductors for windows applications: Effect of substrate material2010In: International Journal of Advances in Science and Technology, ISSN 2229-5216, Vol. 75, p. 25-30Article in journal (Refereed)
  • 280. Lehto, Marcus
    et al.
    Bodén, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A multi-stable miniature paraffin actuator2008In: Proceedings of Actuator, p. 864-867Article in journal (Refereed)
  • 281.
    Lehto, Marcus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Division for Electricity and Lightning Research.
    Bodén, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Simu, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Schweitz, Jan-Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A polymeric paraffin microactuator2008In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 17, no 5, p. 1172-1177Article in journal (Refereed)
    Abstract [en]

    Paraffin wax is a promising material in microactuators not only because of its ability of producing large displacements and high forces at the same time but also because of the variety of manufacturing techniques available. In this paper, a simple actuator based on paraffin wax as the active material is fabricated and tested. Ultraviolet-curable epoxy is used in a technique combining simultaneous moulding and liquid-phase photopolymerization in a single-process step to build the stiff part of the actuator body. A heater is integrated in the paraffin reservoir, and a polyimide tape is used as the deflecting membrane. Thermornechanical analysis of the paraffin wax shows that it exhibits a volume expansion of 10%, including phase transitions and linear expansion. As for the actuator, a stroke of 90 mu m is obtained for the unloaded device, whereas 37 mu m is recorded with a 0.5-N contact load at a driving voltage of 0.71 V and a frequency of 1/32 Hz. The actuator can be used in microsystems, where both large strokes and forces are needed. The low-cost materials and low driving voltage also makes it suitable for disposable systems.

  • 282.
    Lehto, Marcus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Bodén, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Simu, Urban
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Schweitz, Jan-Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Rapid prototyping of a polymeric paraffin microactuator2008In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 17, no 5, p. 1172-1177Article in journal (Refereed)
    Abstract [en]

    Paraffin wax is a promising material in microactuators not only because of its ability of producing large displacements and high forces at the same time but also because of the variety of manufacturing techniques available. In this paper, a simple actuator based on paraffin wax as the active material is fabricated and tested. Ultraviolet-curable epoxy is used in a technique combining simultaneous moulding and liquid-phase photopolymerization in a single-process step to build the stiff part of the actuator body. A heater is integrated in the paraffin reservoir, and a polyimide tape is used as the deflecting membrane. Thermomechanical analysis of the paraffin wax shows that it exhibits a volume expansion of 10%, including phase transitions and linear expansion. As for the actuator, a stroke of 90 mum is obtained for the unloaded device, whereas 37 mum is recorded with a 0.5-N contact load at a driving voltage of 0.71 V and a frequency of 1/32 Hz. The actuator can be used in microsystems, where both large strokes and forces are needed. The low-cost materials and low driving voltage also makes it suitable for disposable systems.

  • 283.
    Lehto, Marcus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Schweitz, Jan-Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Binary mixtures of n-alkanes for tunable thermohydraulic microactuators2007In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 16, no 3, p. 728-733Article in journal (Refereed)
    Abstract [en]

    The two objectives of this paper are related to the use of n-alkanes in actuators. The first objective is to study the thermomechanics of binary mixtures of dotriacontane and hexatriacontane to see if a quasi-stable thermal expansion can be obtained, and the second one is to find the correspondence between dilatometry [pressure, volume, and temperature (pVT) measurement] and differential scanning calorimetry (DSC). Results show that there is indeed a concentration-dependent plateau in the expansion curves and that the width and horizontal position of this can be adjusted. As compared with pure n-alkanes, the plateaus of the mixtures widen by a factor of 2-4, and as compared with pure hexatriacontane, they shift their low-end temperatures by 5 °C to 10 °C, in the 25% to 75% concentration range. The mixtures' plateaus (gathered around 0.06 cm3/g) are about 0.02 cm3/g below those of the pure n-alkanes. It is shown that DSC can be used for a prediction of the thermomechanical properties of the substances, provided that a pVT reference exists, and the fact that the melting point increases with the pressure that is experienced with the dilatometer is considered. The qualitative similarity between the expansion and enthalpy curves is remarkable. About 25% to 30% of the total volume expansion is attributed to the solid-to-solid phase transition; the rest is attributed to thermal expansion and melting.

  • 284.
    Lekholm, Ville
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    High-Temperature Microfluidics for Space Propulsion2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, microfabrication methods and tools for analysis of heated cold-gas microthrusters are presented, with the aim of improving their reliability and performance. Cold-gas thrusters operate by accelerating pressurized gas through a nozzle. These thruster systems are very straightforward in both design and operation, relying on little more than a pressurized tank, a valve, and a nozzle. This makes them suitable for miniaturization, enabling their use on very small spacecraft. However, an inherent drawback with cold-gas thrusters is their low propellant efficiency – in thrusters known as specific impulse, or Isp.  This is compounded by the fact that when reducing length, the volume, e.g., that of the propellant tank, reduces with the cube of the length, meaning that the maximum amount of storable fuel reduces quickly. Hence, maximizing fuel efficiency is even more important in miniaturized systems. Still, because of their other advantages, they remain suitable for many missions. Schlieren imaging – a method of visualizing differences in refractive index – was used thrughout this thesis to visualize exhaust jets from microthrusters, and to find leaks in the components. It was found that effects of the processing of conventionally fabricated silicon nozzles, resulted in a misalignment of up to 3°  from the intended thrust vector, increasing propellant consumption by up to 5%, and potentially causing unintended off-axis acceleration of the spacecraft. Schlieren imaging was also used to verify that the exhaust from thrusters fabricated with close to circular cross-sections was well behaved. These nozzles did not suffer from the previous misalignment issue, and the shape of the cross-section decreased viscous losses. For applications requiring higher temperatures, a microthruster nozzle with an integrated flow sensor was fabricated from tape cast yttria stabilized zirconia. The ceramic substrate enabled heater temperatures of the nozzle exceeding 1000 °C, resulting in an increase in Isp  of 7.5%. Integration of a flow sensor allowed the elimination of couplings and reduced the number of interfaces, thereby reducing the overall risk of failure. Close integration of the sensor allowed moving the point of measurement closer to the nozzle, enabling improved reliability of the measurements of the propellant consumption. The temperature of the heater, in combination with the ion conductive properties of the substrate proved to be a limiting factor in this design. Two routes were explored to overcome these problems. One was to use the temperature dependence of the ion conductivity as a sensing principle, thereby demonstrating a completely new flow sensor principle, which results in better calibration, tighter integration, and 9 orders of magnitude stronger signal. The other was using hafnium oxide, or hafnia, as a structural material for high-temperature micro-electromechanical systems. This involved developing a recipe for casting hafnia ceramic powder, and determining the Young's modulus and thermal shock resistance of the cast samples, as well as studying the minimum feature size and maximum aspect ratio of cast microstructures.

    List of papers
    1. Schlieren Imaging of Microthruster Exhausts for Qualitative and Quantitative Analysis
    Open this publication in new window or tab >>Schlieren Imaging of Microthruster Exhausts for Qualitative and Quantitative Analysis
    2012 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 23, no 8, p. 085403-Article in journal (Refereed) Published
    Abstract [en]

    Abstract. Schlieren imaging is a method used to visualize differences in refractiveindex within a medium. It is a powerful and straightforward tool for sensitiveand high-resolution visualization of, e.g., gas flows. Here, heated cold gasmicrothrusters were studied with this technique. The thrusters are manufacturedusing microelectromechanical systems technology, and measure 22×22×0.85 mm. Thenozzles are approximately 20 µm wide at the throat, and 350 µm wide at the exit.Through these studies, verification of the functionality of the thrusters, and directvisualization and of the thruster exhausts was possible. At atmospheric pressure,slipping of the exhaust was observed, due to severe overexpansion of the nozzle. Invacuum (3 kPa), the exhaust was imaged while feed pressure was varied from 100 to450 kPa. The nozzle was overexpanded, and the flow was seen to be supersonic. Theshock cell period was linearly dependent on feed pressure, ranging from 320 to 610 µm.With activated heaters, the shock cell separation increased. The effect of the heaterswas more prominent at low feed pressure, and an increase in specific impulse of 20%was calculated. It was also shown that schlieren imaging can be used to detect leaks,making it a valuable, safe, and noninvasive aid in quality control of the thrusters.

    Place, publisher, year, edition, pages
    Institute of Physics (IOP), 2012
    Keywords
    Schlieren imaging, microthrusters, MEMS, shock cells
    National Category
    Other Engineering and Technologies not elsewhere specified
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-186252 (URN)10.1088/0957-0233/23/8/085403 (DOI)000306366600039 ()
    Funder
    VINNOVA
    Available from: 2012-11-29 Created: 2012-11-28 Last updated: 2017-12-07Bibliographically approved
    2. Investigation of exhausts from fabricated silicon micronozzles with rectangular and close to rotationally symmetric cross sections
    Open this publication in new window or tab >>Investigation of exhausts from fabricated silicon micronozzles with rectangular and close to rotationally symmetric cross sections
    2013 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 23, no 10, p. 105001-Article in journal (Refereed) Published
    Abstract [en]

    Close to rotationally symmetric in-plane silicon micronozzles with throat and exit diameters of 45 and 260 µm, respectively, have been fabricated using semi-isotropic SF6 etching through an array mask utilizing microloading and reactive ion etching lag. Comparison with nozzles fabricated using deep reactive ion etching (DRIE) and having a rectangular cross-section but a similar hydraulic diameter in the throat, showed that the Reynolds numbers were almost equal even though the DRIE-etched nozzle had an almost five times larger cross-sectional area, hence implying less viscous losses and higher efficiency with the nearly symmetrical nozzles. The nozzle shapes have been studied using x-ray computed tomography. Comparison of the nozzles' exhaust jets using schlieren imaging, showed that the rectangular nozzles' jets deviate from the nozzle axis direction. It is believed that it is caused by the inclined side walls resulting from the DRIE etching. The results from intentionally misaligning the wafers, each containing half a nozzle, 50 µm parallel with or perpendicular to the nozzle axis, showed that the exhaust deviated and widened, respectively. The findings show that the nozzle symmetry affects both the shape and the pointing direction of the exhaust and that schlieren imaging is a powerful tool for determining nozzle thrust vector deviations.

    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-186774 (URN)10.1088/0960-1317/23/10/105001 (DOI)000324672700002 ()
    Available from: 2012-11-29 Created: 2012-11-29 Last updated: 2017-12-07Bibliographically approved
    3. High-temperature zirconia microthruster with integrated flow sensor
    Open this publication in new window or tab >>High-temperature zirconia microthruster with integrated flow sensor
    Show others...
    2013 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 23, no 5, p. 055004-Article in journal (Refereed) Published
    Abstract [en]

    This paper describes the design, fabrication and characterization of a ceramic, heated cold-gas microthruster device made with silicon tools and high temperature co-fired ceramic processing. The device contains two opposing thrusters, each with an integrated calorimetric propellant flow sensor and a heater in the stagnation chamber of the nozzle. The exhaust from a thruster was photographed using schlieren imaging to study its behavior and search for leaks. The heater elements were tested under a cyclic thermal load and to the maximum power before failure. The nozzle heater was shown to improve the efficiency of the thruster by 6.9%, from a specific impulse of 66 to 71 s, as calculated from a decrease of the flow rate through the nozzle of 13%, from 44.9 to 39.2 sccm. The sensitivity of the integrated flow sensor was measured to 0.15 m Omega sccm(-1) in the region of 0-15 sccm and to 0.04 m Omega sccm(-1) above 20 sccm, with a zero-flow sensitivity of 0.27 m Omega sccm(-1). The choice of yttria-stabilized zirconia as a material for the devices makes them robust and capable of surviving temperatures locally exceeding 1000 degrees C.

    Keywords
    Keywords: Zirconia, YSZ, HTCC, schlieren imaging, flow sensor, microthruster
    National Category
    Other Engineering and Technologies not elsewhere specified
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-186257 (URN)10.1088/0960-1317/23/5/055004 (DOI)000317739100004 ()
    Funder
    Vinnova
    Available from: 2012-11-28 Created: 2012-11-28 Last updated: 2017-12-07Bibliographically approved
    4. Investigation of a zirconia co-fired ceramic calorimetric microsensor for high-temperature flow measurements
    Open this publication in new window or tab >>Investigation of a zirconia co-fired ceramic calorimetric microsensor for high-temperature flow measurements
    2015 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 25, no 6, article id 065014Article in journal (Refereed) Published
    Abstract [en]

    This paper describes the design, fabrication and characterization of a flow sensor for high-temperature, or otherwise aggressive, environments, like, e.g. the propulsion system of a small spacecraft. The sensor was fabricated using 8 mol% yttria stabilized zirconia (YSZ8) high-temperature co-fired ceramic (HTCC) tape and screen printed platinum paste. A calorimetric flow sensor design was used, with five 80 mu m wide conductors, separated by 160 mu m, in a 0.4 mm wide, 0.1 mm deep and 12.5 mm long flow channel. The central conductor was used as a heater for the sensor, and the two adjacent conductors were used to resistively measure the heat transferred from the heater by forced convection. The two outermost conductors were used to study the influence of an auxiliary heat source on the sensor. The resistances of the sensor conductors were measured using four-point connections, as the gas flow rate was slowly increased from 0 to 40 sccm, with different power supplied through the central heater, as well as with an upstream or downstream heater powered. In this study, the thermal and electrical integrability of microcomponents on the YSZ8 substrate was of particular interest and, hence, the influence of thermal and ionic conduction in the substrate was studied in detail. The effect of the ion conductivity of YSZ8 was studied by measuring the resistance of a platinum conductor and the resistance between two adjacent conductors on YSZ8, in a furnace at temperatures from 20 to 930 degrees C and by measuring the resistance with increasing current through a conductor. With this design, the influence of ion conductivity through the substrate became apparent above 700 degrees C. The sensitivity of the sensor was up to 1 m Omega sccm(-1) in a range of 0-10 sccm. The results show that the signal from the sensor is influenced by the integrated auxiliary heating conductors and that these auxiliary heaters provide a way to balance disturbing heat sources, e.g. thrusters or other electronics, in conjunction with the flow sensor.

    National Category
    Other Engineering and Technologies
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-246059 (URN)10.1088/0960-1317/25/6/065014 (DOI)000354803000014 ()
    Available from: 2015-03-02 Created: 2015-03-02 Last updated: 2017-12-04Bibliographically approved
    5. A high-temperature calorimetric flow sensor employing ion conduction in zirconia
    Open this publication in new window or tab >>A high-temperature calorimetric flow sensor employing ion conduction in zirconia
    2015 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 106, no 19, article id 194103Article in journal, Letter (Refereed) Published
    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2015
    Keywords
    Calorimetric flow sensor, Ion conductivity, Zirconia, YSZ8
    National Category
    Ceramics Embedded Systems Condensed Matter Physics
    Research subject
    Engineering Science with specialization in Microsystems Technology
    Identifiers
    urn:nbn:se:uu:diva-246105 (URN)10.1063/1.4921051 (DOI)000355008100059 ()
    Funder
    Swedish National Space Board
    Available from: 2015-03-02 Created: 2015-03-02 Last updated: 2017-12-04Bibliographically approved
    6. Hafnium oxide in high-temperature microelectromechanical systems
    Open this publication in new window or tab >>Hafnium oxide in high-temperature microelectromechanical systems
    (English)Manuscript (preprint) (Other academic)
    National Category
    Other Engineering and Technologies
    Identifiers
    urn:nbn:se:uu:diva-246061 (URN)
    Available from: 2015-03-02 Created: 2015-03-02 Last updated: 2015-04-17
  • 285.
    Lekholm, Ville
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Ericson, Fredric
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Palmer, Kristoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Greger, Thornell
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Ceramic microcomponents for high-temperature fluidics2010In: Technical DigestPowerMEMS 2010, The 10th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications, Leuven, Belgium, December 1-3, 2010: Poster Sessions, 2010, p. 291-294Conference paper (Refereed)
    Abstract [en]

    For aggressive environments, the material properties of silicon become a limitation. Macroscopically, ceramics are as abundant for high-temperature applications as is silicon in miniaturized systems, but this group of materials has been little exploited for MEMS components. A major reason is the lack of means for high-resolution structuring. This paper describes the application of silicon-based manufacturing processes in the fabrication of ceramic yet truly micromechanical structures and devices for very high-temperature applications, and demonstrates the technique’s implementation in, and significance for, high-temperature microfluidics. Embossing of structures down to 2 µm wide is demonstrated, as well as deep embossing (50 µm), punching through 15 µm tape, and lamination of structured layers. The resulting samples survive temperatures of 1400ºC.

  • 286.
    Lekholm, Ville
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Persson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Hafnium oxide in high-temperature microelectromechanical systemsManuscript (preprint) (Other academic)
  • 287.
    Lekholm, Ville
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Palmer, Kristoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Ericson, Fredric
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Ceramic cold gas microthruster with integrated flow sensor2011In: PowerMEMS 2011 Technical digest: The 11th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications / [ed] Young-Ho Cho, Daejeon, Republic of Korea: Cell Bench Research Center, KAIST , 2011, p. 167-170Conference paper (Refereed)
    Abstract [en]

    For aggressive environments, the material properties of silicon become a limitation. Macroscopically, ceramics are as common for high-temperature applications as is silicon in miniaturized systems, but this group of materials has been little exploited for MEMS components. This paper describes the  design, manufacturing and characterization of a ceramic, heated cold-gas microthruster with integrated flow sensor, using HTCC processing and silicon tools. The calorimetric flow sensor is integrated in the structure, and heaters are embedded in the stagnation chamber of the nozzle. The heater was shown to improve the efficiency of the thruster, as confirmed by measurements of the flow rate. Flow rate changes were seen as changes in resistance of the fabricated flow sensor. The choice of yttria stabilized zirconia as material for the components make them robust and capable of withstanding  very high temperatures. Samples have been shown  capable of achieving temperatures locally exceeding 1000ºC.

  • 288.
    Lekholm, Ville
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Palmer, Kristoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Johansson, Håkan
    Rangsten, Pelle
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Verifying microexhausts with schlieren imaging2010In: Proceedings of the 2nd International Conference on Space Propulsion, San Sebastián, Spain, May 3-6, 2010, 2010Conference paper (Refereed)
    Abstract [en]

    Schlieren imaging is a method to visualize differences in refractive index within a medium. It is an inexpensive, yet powerful and straightforward tool, for sensitive and high-resolution visualization of gas flows. Here, heated cold gas microthrusters were studied with schlieren imaging techniques. The thruster chips are manufactured using MEMS technology, and measure 22*22*0.85 mm. The nozzles are approximately 20 µm wide at the throat, and 350 µm wide at the exit. Through these studies, verification and direct visualization of the functionality of the thrusters were possible. At atmospheric pressure, slipping of the exhaust was observed, due to the severe overexpansion of the nozzle. In vacuum, the nozzle was underexpanded, and the flow was seen to be supersonic. There was a measurable change in the exhaust with heaters activated. It was also shown that the method can be used to detect leaks, making it a valuable, quick, safe, and inexpensive aid in quality control of the thrusters.

  • 289.
    Lekholm, Ville
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Palmer, Kristoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Schlieren Imaging of Microthruster Exhausts for Qualitative and Quantitative Analysis2012In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 23, no 8, p. 085403-Article in journal (Refereed)
    Abstract [en]

    Abstract. Schlieren imaging is a method used to visualize differences in refractiveindex within a medium. It is a powerful and straightforward tool for sensitiveand high-resolution visualization of, e.g., gas flows. Here, heated cold gasmicrothrusters were studied with this technique. The thrusters are manufacturedusing microelectromechanical systems technology, and measure 22×22×0.85 mm. Thenozzles are approximately 20 µm wide at the throat, and 350 µm wide at the exit.Through these studies, verification of the functionality of the thrusters, and directvisualization and of the thruster exhausts was possible. At atmospheric pressure,slipping of the exhaust was observed, due to severe overexpansion of the nozzle. Invacuum (3 kPa), the exhaust was imaged while feed pressure was varied from 100 to450 kPa. The nozzle was overexpanded, and the flow was seen to be supersonic. Theshock cell period was linearly dependent on feed pressure, ranging from 320 to 610 µm.With activated heaters, the shock cell separation increased. The effect of the heaterswas more prominent at low feed pressure, and an increase in specific impulse of 20%was calculated. It was also shown that schlieren imaging can be used to detect leaks,making it a valuable, safe, and noninvasive aid in quality control of the thrusters.

  • 290.
    Lekholm, Ville
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Persson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Investigation of a zirconia co-fired ceramic calorimetric microsensor for high-temperature flow measurements2015In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 25, no 6, article id 065014Article in journal (Refereed)
    Abstract [en]

    This paper describes the design, fabrication and characterization of a flow sensor for high-temperature, or otherwise aggressive, environments, like, e.g. the propulsion system of a small spacecraft. The sensor was fabricated using 8 mol% yttria stabilized zirconia (YSZ8) high-temperature co-fired ceramic (HTCC) tape and screen printed platinum paste. A calorimetric flow sensor design was used, with five 80 mu m wide conductors, separated by 160 mu m, in a 0.4 mm wide, 0.1 mm deep and 12.5 mm long flow channel. The central conductor was used as a heater for the sensor, and the two adjacent conductors were used to resistively measure the heat transferred from the heater by forced convection. The two outermost conductors were used to study the influence of an auxiliary heat source on the sensor. The resistances of the sensor conductors were measured using four-point connections, as the gas flow rate was slowly increased from 0 to 40 sccm, with different power supplied through the central heater, as well as with an upstream or downstream heater powered. In this study, the thermal and electrical integrability of microcomponents on the YSZ8 substrate was of particular interest and, hence, the influence of thermal and ionic conduction in the substrate was studied in detail. The effect of the ion conductivity of YSZ8 was studied by measuring the resistance of a platinum conductor and the resistance between two adjacent conductors on YSZ8, in a furnace at temperatures from 20 to 930 degrees C and by measuring the resistance with increasing current through a conductor. With this design, the influence of ion conductivity through the substrate became apparent above 700 degrees C. The sensitivity of the sensor was up to 1 m Omega sccm(-1) in a range of 0-10 sccm. The results show that the signal from the sensor is influenced by the integrated auxiliary heating conductors and that these auxiliary heaters provide a way to balance disturbing heat sources, e.g. thrusters or other electronics, in conjunction with the flow sensor.

  • 291.
    Lekholm, Ville
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Persson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Palmer, Kristoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Ericson, Fredric
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    High-temperature zirconia microthruster with integrated flow sensor2013In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 23, no 5, p. 055004-Article in journal (Refereed)
    Abstract [en]

    This paper describes the design, fabrication and characterization of a ceramic, heated cold-gas microthruster device made with silicon tools and high temperature co-fired ceramic processing. The device contains two opposing thrusters, each with an integrated calorimetric propellant flow sensor and a heater in the stagnation chamber of the nozzle. The exhaust from a thruster was photographed using schlieren imaging to study its behavior and search for leaks. The heater elements were tested under a cyclic thermal load and to the maximum power before failure. The nozzle heater was shown to improve the efficiency of the thruster by 6.9%, from a specific impulse of 66 to 71 s, as calculated from a decrease of the flow rate through the nozzle of 13%, from 44.9 to 39.2 sccm. The sensitivity of the integrated flow sensor was measured to 0.15 m Omega sccm(-1) in the region of 0-15 sccm and to 0.04 m Omega sccm(-1) above 20 sccm, with a zero-flow sensitivity of 0.27 m Omega sccm(-1). The choice of yttria-stabilized zirconia as a material for the devices makes them robust and capable of surviving temperatures locally exceeding 1000 degrees C.

  • 292.
    Lekholm, Ville
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Rämme, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Seeing the invisible with schlieren imaging2011In: Physics Education, ISSN 0031-9120, E-ISSN 1361-6552, Vol. 46, no 3, p. 294-297Article in journal (Refereed)
    Abstract [en]

    Schlieren imaging is a method for visualizing differences in refractive index as caused by pressure or temperature non-uniformities within a medium, or as caused by the mixing of two fluids. It is an inexpensive yet powerful and straightforward tool for sensitive and high-resolution visualization of otherwise invisible phenomena. In this article, application of the method to liquid membranes, sonar pulses and microscopic gas flows is used to illustrate its usefulness and versatility in physics education and research.

  • 293.
    Lenshof, Andreas
    et al.
    Lund University.
    Tenje, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Lundgren, Maria
    Skåne University Hospital.
    Svärd-Nilsson, Ann-Margret
    Skåne University Hospital.
    Kjeldsen-Kragh, Jens
    Skåne University Hospital.
    Åberg, Lena
    Skåne University Hospital.
    Laurell, Thomas
    Lund University.
    Removal of proteins from blood using acoustophoresis2014Conference paper (Refereed)
  • 294.
    Lindeberg, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    High aspect ratio “multiple wire” microvias in flexible PCBs2009In: Circuit world, ISSN 0305-6120, E-ISSN 1758-602X, Vol. 35, no 4, p. 18-21Article in journal (Refereed)
  • 295.
    Lindeberg, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Multiple nanowire via interconnects in flexible printed circuit boards2009In: Smart Systems Integration 2009, 2009, p. 6-11Conference paper (Other academic)
  • 296.
    Lindeberg, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Yousef, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Röjdegård, Henrik
    Martin, Hans
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Materialvetenskap.
    Flexible PCB Vertical Thermopile IR Sensor Proc. Solid-State Sensors, Actuators and Microsystems Conference2007Conference paper (Refereed)
  • 297.
    Liu, Zhenhua
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Fornell, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Barbe, Laurent
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Tenje, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    On-chip background dilution in droplets with high particle recovery using acoustophoresis2019In: Biomicrofluidics, ISSN 1932-1058, E-ISSN 1932-1058, Vol. 13, article id 064123Article in journal (Refereed)
    Abstract [en]

    Droplet microfluidics has shown great potential for on-chip biological and chemical assays. However, fluid exchange in droplet microfluidics with high particle recovery is still a major bottleneck. Here, using acoustophoresis, we present for the first time a label-free method to achieve continuous background dilution in droplets containing cells with high sample recovery. The system comprises droplet generation, acoustic focusing, droplet splitting, picoinjection, and serpentine mixing on the same chip. The capacities of the picoinjection and the droplet split to dilute the background fluorescent signal in the droplets have been characterized. The sample recovery at different droplet split ratios has also been characterized. The results show a maximum of 4.3-fold background dilution with 87.7% particle recovery. We also demonstrated that the system can be used to dilute background fluorescent signal in droplets containing either polystyrene particles or endothelial cells.

  • 298.
    Liu, Zhenhua
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Fornell, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Tenje, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    A continuous on-chip droplet washing platform with high bead recovery by acoustofluidics2019Conference paper (Other academic)
    Abstract [en]

    Acoustofluidics is a promising technology for manipulation of fluids and particles in microchannels, and the technology has the ability to sort beads and cells in continuous flow with very high efficiency. Recently acoustofluidics has also been applied in segmental flow for positioning beads inside droplets. Compared with single-phase systems, droplet microfluidics has the advantages of faster reactions, lower cross-contamination and higher throughput. Moreover, the small size of the droplets makes them ideal as cultivation and reaction vials for single cell analysis. However, as the droplets are so small one challenge is to wash the droplets before image analysis. P. Mary et al. developed a microfluidic platform for droplet wash, whichis based on electrocoalescence and droplet break-ups with equal volume. The background noise was decreased significantly, however the recovery of the encapsulated cells was low. Alternative solutions have been presented by H. Lee et al. and S.R. Doonan et al. but as the bead recovery is controlled via magnetophoresis, the technology is only applicable to magnetic samples. Here we present a droplet microfluidic platform that enables background dilution with high bead recovery in a label-free manner using acoustophoresis.

  • 299.
    Liu, Zhenhua
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Fornell, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Tenje, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Droplet Dilution Unit Operation Including Bead Washing Using Integrated Acoustophoresis2019Conference paper (Other academic)
    Abstract [en]

    This paper presents a microfluidic platform for on-chip droplet dilution where the bead recovery also can be controlled. The droplets containing 10 µm polystyrene beads can be diluted with high bead recovery. This platform involves 5 steps for on-chip dilution of the droplets: droplet generation, bead focusing, droplet splitting, pico-injection and serpentine mixing. Background signal in the droplets is significantly reduced with maintained bead recovery by this on-chip dilution method. The technology is applicable to many types of samples and does not require any labelling of the bioparticles.

  • 300. Liu, Zhenhua
    et al.
    Xu, Wenchao
    Hou, Zining
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A Rapid Prototyping Technique for Microfluidics with High Robustness and Flexibility2016In: Micromachines, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 7, no 11, article id 201Article in journal (Refereed)
    Abstract [en]

    In microfluidic device prototyping, master fabrication by traditional photolithography is expensive and time-consuming, especially when the design requires being repeatedly modified to achieve a satisfactory performance. By introducing a high-performance/cost-ratio laser to the traditional soft lithography, this paper describes a flexible and rapid prototyping technique for microfluidics. An ultraviolet (UV) laser directly writes on the photoresist without a photomask, which is suitable for master fabrication. By eliminating the constraints of fixed patterns in the traditional photomask when the masters are made, this prototyping technique gives designers/researchers the convenience to revise or modify their designs iteratively. A device fabricated by this method is tested for particle separation and demonstrates good properties. This technique provides a flexible and rapid solution to fabricating microfluidic devices for non-professionals at relatively low cost.

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