uu.seUppsala University Publications
Change search
Refine search result
12 1 - 50 of 72
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Andersson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Ek, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hedman, Ludvig
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sehlstedt, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Stocklassa, Jesper
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Snögren, Pär
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Pettersson, Victor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Larsson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Vizuete, Olivier
    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.
    Thin film metal sensors in fusion bonded glass chips for high-pressure microfluidics2017In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 27, no 1, article id 015018Article in journal (Refereed)
    Abstract [en]

    High-pressure microfluidics offers fast analyses of thermodynamic parameters for compressed process solvents. However, microfluidic platforms handling highly compressible supercritical CO2 are difficult to control, and on-chip sensing would offer added control of the devices. Therefore, there is a need to integrate sensors into highly pressure tolerant glass chips. In this paper, thin film Pt sensors were embedded in shallow etched trenches in a glass wafer that was bonded with another glass wafer having microfluidic channels. The devices having sensors integrated into the flow channels sustained pressures up to 220 bar, typical for the operation of supercritical CO2. No leakage from the devices could be found. Integrated temperature sensors were capable of measuring local decompression cooling effects and integrated calorimetric sensors measured flow velocities over the range 0.5-13.8 mm/s. By this, a better control of high-pressure microfluidic platforms has been achieved.

  • 2.
    Andersson, Martin
    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.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Fracture strength of glass chips for high-pressure microfluidics2016In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 26, no 9, article id 095009Article in journal (Refereed)
    Abstract [en]

    High-pressure microfluidics exposes new areas in chemistry. In this paper, the reliability of transparent borosilicate glass chips is investigated. Two designs of circular cavities are used for fracture strength tests, either 1.6 mm wide with rounded corners to the fluid inlets, or 2.0 mm wide with sharp inlet corners. Two kinds of tests are done, either short-term,e.g. pressurization to fracture at room temperature, or long-term, with fracture at constant pressurization for up to one week, in the temperature region 11–125 °C. The speed of crack fronts is measured using a high-speed camera. Results show fracture stresses in the range of 129 and 254 MPa for short-term measurements. Long-term measurements conclude the presences of a temperature and stress dependent delayed fracture. For a reliability ofone week at 11–38 °C, a pressure limit is found at the lower end of the short-term measurements, or 15% lower than the average. At 80 °C, this pressure limit is 45% lower. Crack speeds are measured to be 10−5 m s-1 during short-term fracture. These measurements are comparable with estimations based on slow crack growth and show that the growth affects the reliability of glass chips. This effect is strongly affected by high temperatures, thus lowers the operating window of high-pressure glass microfluidic devices.

  • 3.
    Anderås, Emil
    et al.
    St Jude Medical, Cardiovascular Division, Uppsala.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Lamb wave resonant pressure micro-sensor utilizing a thin-film aluminium nitride membrane2011In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 21, no 8, p. 085010-Article in journal (Refereed)
    Abstract [en]

    In this work, pressure sensitivities of aluminium nitride (AlN) thin film plate acoustic resonators (FPAR) operating at the lowest-order symmetric (S0), the first-order asymmetric (A1) as well as the first-order symmetric (S1) Lamb modes are theoretically and experimentally studied in a comparative manner. The finite element method analysis has also been performed to get a further insight into the FPAR pressure sensitivity. The theoretical predictions are found to be in good agreement with the experiment. The S0 Lamb mode is identified as the most pressure-sensitive FPAR mode, while the A1 and S1 modes are found to be much less sensitive. Further, the S0 and the A1 modes exhibit almost equal temperature sensitivities, which can be exploited to eliminate the temperature drift by comparing the resonance frequencies of the latter two modes.

  • 4.
    Arapan, Lilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    An intermode-coupled thin-film micro-acoustic resonator2012In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 22, no 8, p. 085004-Article in journal (Refereed)
    Abstract [en]

    A novel concept for the development of thin-film micro-acoustic resonators based on the coupling between different plate acoustic modes was demonstrated. The basic principles for the design and fabrication of intermode-coupled plate acoustic wave resonators on c-textured thin AlN films were presented and first experimental proof of coupling between laterally propagating waves and BAW was demonstrated. The experimental results demonstrate that the grating-assisted intermode coupling can be employed in high-frequency resonators inheriting the low dispersive nature of the S0 mode in combination with the energy localization in the plate bulk typical for the fundamental thickness shear resonance.

  • 5.
    Bejhed, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Nguyen, Hugo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Åstrand, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Köhler, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Numerical modeling and verification of gas flow through a network of crossed narrow v-grooves2006In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 16, no 10, p. 2006-2013Article in journal (Refereed)
    Abstract [en]

    The gas flow through a network of crossing thin micro-machined channels has been successfully modeled and simulated. The crossings are formed by two sets of v-grooves that intersect as two silicon wafers are bonded together. The gas is distributed from inlets via a manifold of channels to the narrow v-grooves. The narrow v-grooves could work as a particle filter. The fluidic model is derived from the Navier–Stokes equation and assumes laminar isothermal flow and incorporates small Knudsen number corrections and Poiseuille number calculations. The simulations use the finite element method. Several elements of the full crossing network model are treated separately before lumping them together: the straight v-grooves, a single crossing in an infinite set and a set of exactly four crossings along the flow path. The introduction of a crossing effectively corresponds to a virtual reduction of the length of the flow path, thereby defining a new effective length. The first and last crossings of each flow path together contribute to a pressure drop equal to that from three ordinary crossings. The derived full network model has been compared to previous experimental results on several differently shaped crossed v-groove networks. Within the experimental errors, the model corresponds to the mass flow and pressure drop measurements. The main error source is the uncertainty in v-groove width which has a profound impact on the fluidic behavior.

  • 6.
    Bejhed, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rangsten, Pelle
    Köhler, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Demonstration of a single use microsystem valve for high gas pressure applications2007In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 17, no 3, p. 472-481Article in journal (Refereed)
    Abstract [en]

    Demonstrated and characterized here is a single use valve developed for high-pressure applications. Incorporated within the single use valve is a particle filter. The filter serves to remove any particle debris created by the activation process. The valve is solder sealed to be leakage proof. The solder is remelted to obtain activation of the valve. Local heater elements are incorporated on the valve surface together with solder wetting pads. The gas mass flow through the device was evaluated prior to sealing and after activation. The valve was functional at pressures of 100 bar, and opened in less than 10 s with an applied power of 13 W.

  • 7.
    Berglund, Martin
    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.
    Lotfi, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kratz, Henrik
    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.
    Dynamic characterization and modelling of a dual-axis beam steering device for performance understanding, optimization, and control design2013In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 23, no 4, p. 045020-Article in journal (Refereed)
    Abstract [en]

    This paper presents a lumped thermal model of a dual-axis laser micromirror device for beam steering in a free-space optical (FSO) communication system, designed for fractionated spacecraft. An FSO communication system provides several advantages, such as larger bandwidth, smaller size and weight of the communication payload and less power consumption. A dual-axis mirror device is designed and realized using microelectromechanical systems technology. The fabrication is based on a double-sided, bulk micromachining process, where the mirror actuates thermally by joints consisting of v-grooves filled with the SU-8 polymer. The size of the device, consisting of a mirror, which is deflectable versus its frame in one direction, and through deflection of the frame in the other, is 15.4 × 10.4 × 0.3 mm3. In order to further characterize and understand the micromirror device, a Simulink state-space model of the actuator is set up using thermal and mechanical properties from a realized actuator. A deviation of less than 2% between the modelled and measured devices was obtained in an actuating temperature range of 20–200 °C. The model of the physical device was examined by evaluating its performance in vacuum, and by changing physical parameters, such as thickness and material composition. By this, design parameters were evaluated for performance gain and usability. For example, the crosstalk between the two actuators deflecting the mirror along its two axes in atmospheric pressure is projected to go down from 97% to 6% when changing the frame material from silicon to silicon dioxide. A feedback control system was also designed around the model in order to examine the possibility to make a robust control system for the physical device. In conclusion, the model of the actuator presented in this paper can be used for further understanding and development of the actuator system.

  • 8.
    Berglund, Martin
    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 Defence University.
    Thornell, Greger
    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.
    Manufacturing Miniature Langmuir probes by Fusing Platinum Bond Wires2015In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 25, no 10, article id 105012Article in journal (Refereed)
    Abstract [en]

    This paper reports on a novel method for manufacturing microscopic Langmuir probes with spherical tips from platinum bond wires for plasma characterization in microplasma sources by fusing. Here, the resulting endpoints, formed by droplets of a fused wire, are intended to act as a spherical Langmuir probe. For studying the fusing behavior, bond wires were wedge-bonded over a 2 mm wide slit, to emulate the final application, and fused at different currents and voltages. For electrical isolation, a set of wires were coated with a 4 µm thick layer of Parylene before they were fused. After fusing, the gap size, as well as the shape and area of the ends of the remaining stubs were measured. The yield of the process was also investigated, and the fusing event was studied using a high-speed camera for analyzing the dynamics of fusing. Four characteristic tip shapes were observed: spherical, semi-spherical, serpentine shaped and folded. The stub length leveled out at ~420µm. The fusing of the coated wires required a higher power for attaining a spherical shape. Finally, a Parylene coated bond wire was integrated into a stripline split-ring resonator (SSRR) microplasma source, and fused to form two Langmuir probes with spherical endpoints. These probes were used for measuring the I-V characteristics of a plasma generated by the SSRR. In a voltage range between -60 V and 60 V, the fused stubs exhibited the expected behavior of spherical Langmuir probes and will be considered for future integration.

  • 9.
    Bjurström, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Wingqvist, Gunilla
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Temperature compensation of liquid FBAR sensors2007In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 17, no 3, p. 651-658Article in journal (Refereed)
    Abstract [en]

    In this work we demonstrate a practically complete temperature compensation of the second harmonic shear mode in a composite Al/AlN/Al/SiO2 thin film bulk acoustic resonator (FBAR) in the temperature range 25 °C–95 °C. The main advantages of this mode are its higher Q value in liquids as well as its higher frequency and hence higher resolution for sensor applications. For comparative reasons the non-compensated fundamental shear mode is also included in these studies. Both modes have been characterized when operated both in air and in pure water. Properties such as Q value, electromechanical coupling, dissipation and sensitivity are studied. An almost complete temperature compensation of the second harmonic shear mode was observed for an oxide thickness of 1.22 µm for an FBAR consisting of 2 µm thick AlN and 200 nm thick Al electrodes. Thus, the measured temperature coefficient of frequency (TCF) in air for the non-compensated fundamental shear mode (1.25 GHz) varied between −31 and −36 ppm °C−1 over the above temperature range while that of the compensated second harmonic shear mode (1.32 GHz) varied between +2 ppm °C−1 and −2 ppm °C−1 over the same temperature interval. When operated in pure water the former type shows a Q value and coupling coefficient, k2t, around 180 and 2%, respectively, whereas for the second harmonic these are 230 and 1.4%, respectively.

  • 10.
    Bodén, Roger
    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.
    Schweitz, Jan-Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Simu, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A metallic micropump for high-pressure microfluidics2008In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 18, no 11, p. 115009-Article in journal (Refereed)
    Abstract [en]

    This paper presents one of the strongest mechanical sub-cm(3) sized micropumps for microfluidics. It consists of two active valves and one pumping chamber, each operated by a paraffin actuator that is driven by a low-voltage square pulse waveform. The pump is fabricated in a simple process using parylene-coated stainless steel stencils, paraffin and copper clad polyimide. When driving the pump at 0.07 Hz and 2.0 V (0.8 W) per actuator, it pumped water without leakage at a flow rate of 0.75 mu L min(-1) up to above 50 bar (5 MPa) back-pressure. The frequency dependence was evaluated and a maximum flow rate of 1 mu L min(-1) at 0.21 Hz and 1.8 V was observed. A thermomechanical FEM analysis, which was in good agreement with experiments at low frequencies, predicts the behaviour at higher frequencies.

  • 11.
    Bodén, Roger
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Lehto, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Margell, Joakim
    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, Micro Structural Technology.
    Schweitz, Jan-Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    On-chip liquid storage and dispensing for lab-on-a-chip applications2008In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 18, no 7, p. 075036-Article in journal (Refereed)
    Abstract [en]

    This work presents novel components for on-chip storage and dispensing inside a lab-on-a-chip (LOC) for applications in immunoassay point-of-care testing (POCT), where incubation and washing steps are essential. It involves easy-to-use on-chip solutions for the sequential thermo-hydraulic actuation of liquids. The novel concept of combining the use of a rubber plug, both as a non-return valve cap and as a liquid injection interface of a sealed reservoir, allows simple filling of a sterilized cavity, as well as the storage and dispensing of reagent and washing buffer liquids. Segmenting the flow with air spacers enables effective rinsing and the use of small volumes of on-chip stored liquids. The chip uses low-resistance resistors as heaters in the paraffin actuator, providing the low-voltage actuation that is preferred for handheld battery driven instruments.

  • 12. Bäcklund, Ylva
    et al.
    Hermansson, K
    Söderbärg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    A suggested mechanism for silicon direct bonding from studying hydrophilic and hydrophobic surfaces1992In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 2, p. 158-160Article in journal (Refereed)
  • 13.
    Bäcklund, Ylva
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rosengren, Lars
    New shapes in (100) Si using KOH and EDP etches1992In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 2, p. 75-79Article in journal (Refereed)
  • 14.
    Cruz, Javier
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Zadeh, S. Hooshmand
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Graells, Tiscar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Univ Autonoma Barcelona, Dept Genet & Microbiol, Barcelona, Spain..
    Andersson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Malmström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Wu, Zhigang G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan, Peoples R China..
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    High pressure inertial focusing for separating and concentrating bacteria at high throughput2017In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 27, no 8, article id 084001Article in journal (Refereed)
    Abstract [en]

    Inertial focusing is a promising microfluidic technology for concentration and separation of particles by size. However, there is a strong correlation of increased pressure with decreased particle size. Theory and experimental results for larger particles were used to scale down the phenomenon and find the conditions that focus 1 mu m particles. High pressure experiments in robust glass chips were used to demonstrate the alignment. We show how the technique works for 1 mu m spherical polystyrene particles and for Escherichia coli, not being harmful for the bacteria at 50 mu l min(-1). The potential to focus bacteria, simplicity of use and high throughput make this technology interesting for healthcare applications, where concentration and purification of a sample may be required as an initial step.

    The full text will be freely available from 2018-06-27 00:00
  • 15.
    Edqvist, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Corradi, Paolo
    Center for Applied Research in Micro Engineering, Scuola Superiore Sant’Anna, Pontedera, Italy.
    A vibrating microcantilever sensor for microrobotic applicationsIn: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439Article in journal (Refereed)
    Abstract [en]

    In order to actively interact with the environment and to perform advanced tasks, microrobots need to be equipped with sensing tools to detect object and obstacles, and eventually manipulate and transport micro-parts. The concept, design, simulations and first characterization of a simple multifunctional microsystem, a vibrating microcantilever, capable of working as touch sensor and potentially as manipulation tool with feedback sensing is presented. The presented microcantilever was designed to be integrated onboard a microrobot of about 3 × 3 × 3 mm3. The microcantilever is applied as a sensing antenna on the microrobot in order to recognize objects or obstacles through direct contact, causing a voltage drop in a feedback layer. The microcantilever produced is 2.85×0.45×0.098 mm, and the experiments verified that it could be used as a contact sensor featuring high sensitivity with extremely low power consumption and good mass-manufacturability.

  • 16.
    Edqvist, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hedlund, Emma
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Design and manufacturing considerations of low voltage multilayer P(VDF-TrFE) actuators2009In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 19, no 11, p. 115019-Article in journal (Refereed)
    Abstract [en]

    An actuator unit consisting of three multilayered cantilevers with poly(vinylidene fluoride-trifluoroethylene) on top of a flexible printed circuit board substrate is presented. The multilayer structure has five active polymer layers and six electrodes with an alternating ground and phase configuration. Different aspects regarding processing and deflection advantages, depending on which side of the substrate the multilayer structure is manufactured, are discussed.  One of the cantilever configurations is dynamically modelled using a finite element software and the results are compared to measured values. Because of the combination of a multilayer design and the resonant driving mode, the actuators could be powered by solar cells or used in portable electronics. A 2 V sine wave signal resulted in a tip deflection of 56 μm. To test the unit as a conveyer, speed measurements were conducted. With a 2.5 V square wave signal the speed was 29 µm/s whereas a 8 V signal resulted in 732 µm/s. Motion in all four directions could be confirmed by tuning the frequency of a 10 V square wave signal from 640 Hz to 740 Hz.

  • 17.
    Edqvist, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Snis, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Casanova Mohr, Raimon
    SiC, Electronics Department, University of Barcelona, Barcelona, Spain.
    Scholz, Oliver
    IBMT, Fraunhofer Institute for Biomedical Engineering, St Ingbert, Germany.
    Corradi, Paolo
    Scuola Superiore Sant’Anna, Pisa, Italy.
    Gao, Jianbo
    IBMT, Fraunhofer Institute for Biomedical Engineering, St Ingbert, Germany.
    Di´eguez, Angel
    SiC, Electronics Department, University of Barcelona, Barcelona, Spain.
    Wyrsch, Nicolas
    Institut de Microtechnique, University of Neuchˆatel, Neuchˆatel, Switzerland.
    Johansson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Evaluation of building technology for mass producible millimetre-sized robots using flexible printed circuit boards2009In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 19, no 7, p. 11pp-Article in journal (Refereed)
    Abstract [en]

    Initial tests of a building technology for a compact three-dimensional mass produciblemicrorobot are presented. The 3.9 × 3.9 × 3.3 mm3 sized prototype robot represents amicrosystem with actuators, sensors, energy management and integrated electronics. Theweight of a folded robot is 65 mg and the total volume is less than 23 mm3. The design of theinterfaces of the different modules in the robot, as well as the building technology, isdescribed. The modules are assembled using conductive adhesive with industrial surfacemounting technology on a thin double-sided flexible printed circuit board. The final shape ofthe microrobots is achieved by folding the flexible printed circuit board twice. Electrical andmechanical studies are performed to evaluate the assembly and it is concluded that thetechnology can be used for this type of microsystem. Several issues using the presentedassembly technique are identified and addressed.

  • 18.
    Edqvist, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Snis, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Johansson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Gentle dry etching of P(VDF-TrFE) multilayer micro actuator structures by use of an inductive coupled plasma2008In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 18, no 1, p. 015007-Article in journal (Refereed)
    Abstract [en]

    To fully utilize the actuator properties of poly(vinylidenefluoride) (P(VDF))-based polymers, the electric field has to be rather high and one way to accomplish this, in particular with low voltage drive signals, is to build multilayered structures. This paper focuses on how to structure poly(vinylidenefluoride-trifluoroethylene) P(VDF-TrFE) by presenting an etch method to create multilayered miniaturized actuators, with intermediate aluminium electrodes. To create inter-connect areas for the multilayer electrodes, a modified Bosch process in an inductive couple plasma (ICP) etcher is used to remove all P(VDF-TrFE) not covered by the electrodes. Since each electrode mask is slightly different from the others, the result is a staircase-like inter-electrode contact area that is connected from above using a conductive adhesive. The developed ICP etch results in high selective etching and a good agreement between theoretical and measured capacitance values. The manufactured cantilevers, consisting of a multilayer on top of a flexible printed circuit (FPC) board, were tested and the resonant stroke was confirmed to agree with expected values. The successful establishment of interlayer connections between the electrodes open up the possibility for batch fabrication of cheap low voltage micro actuators built on a standard substrate used in millions of commercial products. 2008 IOP Publishing Ltd.

  • 19. Elwenspoek, M
    et al.
    Smith, Leif
    Hök, Bertil
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Active joints for microrobot limbs1992In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 2, p. 221-223Article in journal (Refereed)
  • 20.
    Enlund, Johannes
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Johansson, Linda
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology .
    Surface Acoustic Wave-induced particle manipulation in a glass microfluidic channelIn: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439Article in journal (Refereed)
  • 21.
    Evander, Mikael
    et al.
    Lund University.
    Tenje, Maria
    Lund University.
    Microfluidic PMMA interfaces for rectangular glass capillaries2014In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 24, no 2, p. 027003-Article in journal (Refereed)
  • 22. Gan, H. Y.
    et al.
    Shan, Xuechuan
    Eriksson, T
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Lok, K
    Lam, Y. C.
    Reduction of droplet volume by controlling actuating waveforms in inkjet printing for micro-pattern formation2009In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 19, no 5, p. 055010-Article in journal (Refereed)
    Abstract [en]

    Inkjet printing has proven to be a promising and flexible process methodology for low cost and drop-on-demand pattern formation in small-scale production of micro-electro-mechanical systems. To optimize the micro-patterns formed by inkjet printing, an accurate control of droplet volume is essential and critical. In this study, an inkjet system with a nozzle driven by a circular piezoelectric element was used to explore the impact of different waveforms on droplet volume. The investigation into this study included the impact of unipolar, bipolar, M-shaped and W-shaped waveforms as well as the effects of their amplitudes and pulse durations. The inkjetting behavior of Newtonian and non-Newtonian fluids under different actuating waveforms was studied in order to obtain a maximum reduction in ejected droplet sizes. An effective reduction of droplet volume in the range of 50-80% was demonstrated. The results of inkjetting PEDOT ink on a polished silicon surface showed that a 50% reduction in line width was achieved.

  • 23. Hedlund, C
    et al.
    Bucht, U
    Söderkvist, J
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Two-dimensional etching diagrams for z-cut quartz1992In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 2, p. 215-217Article in journal (Refereed)
  • 24. Hedlund, C
    et al.
    Lindberg, U
    Söderkvist, UBoJ
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Anisotropic etching of Z-cut quartz1993In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 3, p. 65-73Article in journal (Refereed)
  • 25. Hjort, Klas
    et al.
    Söderkvist, J
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    The Piezoelectric effect of GaAs used for resonant sensors and actuators1994In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 4, p. 28-34Article in journal (Refereed)
  • 26. Hjort, Klas
    et al.
    Söderkvist, J
    Schweitz, J-Å
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Gallium arsenide as a mechanical material1994In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 4, p. 1-13Article in journal (Refereed)
  • 27.
    Hjort, Klas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Huazhong University of Science and Technology.
    Microfluidic mixing and separation2016In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 26, no 1, article id 010402Article in journal (Refereed)
  • 28.
    Johansson, Linda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Enlund, Johannes
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Johansson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Wiklund, M
    Dept of Applied Physics, Albanova/KTH , Stockholm.
    Yantchev, Ventislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Surface acoustic wave-induced precise particle manipulation in a trapezoidal glass microfluidic channel2012In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 22, no 2, p. 025018-Article in journal (Refereed)
    Abstract [en]

    Surface acoustic wave (SAW) excitation of an acoustic field in a trapezoidal glass microfluidic channel for particle manipulation in continuous flow has been demonstrated. A unidirectional interdigital transducer (IDT) on a Y-cut Z-propagation lithium niobate (LiNbO3) substrate was used to excite a surface acoustic wave at approximately 35 MHz. An SU8 layer was used for adhesive bonding of the superstrate glass layer and the substrate piezoelectric layer. This work extends the use of SAWs for acoustic manipulation to also include glass channels in addition to prior work with mainly poly-di-methyl-siloxane channels. Efficient alignment of 1.9 mu m polystyrene particles to narrow nodal regions was successfully demonstrated. In addition, particle alignment with only one IDT active was realized. A finite element method simulation was used to visualize the acoustic field generated in the channel and the possibility of 2D alignment into small nodal regions was demonstrated.

  • 29.
    Jönsson, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Lindberg, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    A planar polymer microfluidic electrocapture device for bead immobilization2006In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 16, no 10, p. 2116-2120Article in journal (Refereed)
    Abstract [en]

    A planar microfluidic electrocapture device that captures and concentrates beads by a local electrical field has been assembled and tested. The device presented also enables on-line observations of electrically manipulated beads in a micro-channel. The design is based on a sandwich construction from a glass substrate and a PMMA-lid, using a patterned polyimide spacer to form the channel. Capture and release of 2 mu m polystyrene beads have been performed successfully at an applied potential of 300 V in 25 min. The captured sample plug and its parabolic shape is studied and discussed. The planar capture device design opens for using the electrocapture principle in future microfluidic tools, e. g. a fluidic switch.

  • 30.
    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.

  • 31.
    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.

  • 32.
    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.

  • 33.
    Klintberg, Lena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    A thermal microactuator made by partial impregnation of polyimide with paraffin2002In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 12, no 6, p. 849-854Article in journal (Refereed)
    Abstract [en]

    We have fabricated and tested thermal, paraffin-impregnated polyimide actuators, utilizing the large volume increase associated with the solid-to-liquid phase transition of paraffin. In the bimorph-like device, the top layer was made porous by ion track technology. Stochastically distributed pores of various lengths (95, 70, 45 and 20 µm) and various lateral coverages (5–45%) were filled with paraffin by liquid substitution or from vacuum, and sealed with epoxy. Actuators, 125 µm thick, 35 mm long and 7 mm wide, have been characterized with respect to tip deflection and load-carrying capacity with one end rigidly clamped. Loaded with 0.6 g or about ten times their own weight at their free end, about 50% of the maximum stroke (17 mm) was still attained.

  • 34.
    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. 

  • 35. 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.

  • 36.
    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.

  • 37.
    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.

  • 38. Lindberg, Ulf
    et al.
    Söderkvist, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Lammerink, T
    Elwenspoek, M
    Quasi-buckling of micromachined beams1993In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439Article in journal (Refereed)
  • 39.
    Lindeberg, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Yousef, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Rödjegård, Henrik
    Martin, Hans
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    A PCB-like Process for Vertically Configured Thermopiles2008In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 18, no 6, p. 065021-Article in journal (Refereed)
    Abstract [en]

    Thermopiles are important components in infrared thermal detectors, thermoelectric generators and thermoelectric coolers. We present a thermopile structure with up to 224 vertically arranged thermocouple legs in a polyimide flex material. The thermopile is optimized for infrared thermal radiation detection and is fabricated using printed circuit board-like (PCB-like) processing. Each thermoelectric leg consists of a bundle of a few hundred sub-micrometre-sized strands of either antimony or nickel. These metal wire bundles were achieved by employing ion track technology on the polyimide foil, resulting in a porous dielectric material. Electrochemical methods were used to grow the thermoelectric materials in the pores. The plating mask was produced in a laminated dry photoresist. A small metal cross section, 20 mu m(2) (1 vol%), ensured a low heat exchange between the two surfaces of the flex. The typical resistance per thermocouple was 34 Omega. A responsivity to irradiance of 4.3 V mm(2) W(-1) was measured when heating with a white light source (irradiance 1 mW mm(-2)).

  • 40.
    Martin, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics.
    Yantchev, Ventsislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics.
    Buried electrode electroacoustic technology for the fabrication of thin film based resonant components2006In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 16, no 9, p. 1869-1874Article in journal (Refereed)
    Abstract [en]

    A fabrication process for thin film electroacoustic devices utilizing buriedelectrodes is presented. A one-step lithography process has been developedto bury electrodes resulting in a planarized surface. The proposedtechnology is expected to bring about a number of benefits concerning theperformance of a variety of thin film electroacoustic devices. With respectto thin film plate acoustic resonators (FPAR), burying the reflectorelectrodes results in improved reflectivity and potentially lowersusceptibility to acousto-migration effects. It is also shown that employingthe proposed technology for the fabrication of both thin film bulk acousticresonators (FBAR) and thin film solidity mounted bulk acoustic resonators(SBAR) eliminates certain macro-structural defects in the piezoelectric filmwhich is a prerequisite for substantially improved device performance andhigher power handling capability. The buried electrode electroacoustic (EA)technology is demonstrated for a thin aluminium nitride (AlN) piezoelectricfilm with electrodes of both molybdenum (Mo) and tungsten (W). The latterhave been primarily chosen because of their high electroacoustic materialquality. Thin film resonant structures produced by this technology arecharacterized and their features are discussed.

  • 41.
    Nguyen, Hugo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Bejhed, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Köhler, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    A solder sealing method for paraffin-filled microcavities2006In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 16, no 11, p. 2369-2374Article in journal (Refereed)
    Abstract [en]

    Demonstrated and investigated here is a method to seal microfluidic systems by soldering. As a particularly difficult case of growing importance, the sealing of openings contaminated with paraffin wax was studied. Solder paste, screen printed on a metallized silicon, substrate was melted locally through application of 6.5 to 10 V to a 5 Ω copper film resistor for a few seconds and found able to drive an intermediate layer of paraffin away and seal a 0.2 mm diameter circular via by wetting to a surrounding copper pad. Although verified to be robust, the process did result in failing seals on excessive heating because of consumption of the pads. Correctly performed, the technique provided a seal at least withstanding a pressure of 8 bar for 8 h at 85ºC.

  • 42.
    Ohlin, Mathias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Fornell, Anna
    Lund University, Lund, Sweden.
    Bruus, Henrik
    Tech Univ Denmark, Lyngby, Denmark.
    Tenje, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab. Lund University, Lund, Sweden.
    Improved positioning and detectability of microparticles in droplet microfluidics using two-dimensional acoustophoresis2017In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 27, no 8, article id 084002Article in journal (Refereed)
    Abstract [en]

    We have fabricated a silicon-glass two-phase droplet microfluidic system capable of generating sub 100 µm-sized,   =  (74  ±  2) µm, spherical droplets at rates of up to hundreds of hertz. By implementing a two-dimensional (2D) acoustophoresis particle-positioning method, we show a fourfold improvement in both vertical and lateral particle positioning inside the droplets compared to unactuated operation. The efficiency of the system has been optimized by incorporating aluminum matching layers in the transducer design permitting biocompatible operational temperatures (<37 °C). Furthermore, by using acoustic actuation, (99.8  ±  0.4)% of all encapsulated microparticles can be detected compared to only (79.0  ±  5.1)% for unactuated operation. In our experiments we observed a strong ordering of the microparticles in distinct patterns within the droplet when using 2D acoustophoresis; to explain the origin of these patterns we simulated numerically the fluid flow inside the droplets and compared with the experimental findings.

  • 43.
    Palmer, Kristoffer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    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.
    A highly integratable silicon thermal gas flow sensor2012In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 22, no 6, p. 065015-Article in journal (Refereed)
    Abstract [en]

    Thermal flow sensors have been designed, fabricated, and characterized. All bulk material in these devices is silicon so that they are integratable in silicon-based microsystems. To mitigate heat losses and to allow for use of corrosive gases, the heating and sensing thin film titanium/platinum elements, injecting and extracting heat, respectively, from the flow, are placed outside the channel on top of a membrane consisting of alternating layers of stress-balancing silicon dioxide and silicon nitride. For the fabrication, an unconventional bond surface protection method using sputter-deposited aluminum instead of thermal silicon dioxide is used in the process steps prior to silicon fusion bonding. A method for performing lift-off on top of the transparent membrane was also developed. The sensors, measuring 9.5 x 9.5 mm(2), are characterized in calorimetric and time-of-flight modes with nitrogen flow rates between 0 sccm and 300 sccm. The maximum calorimetric sensor flow signal and sensitivity are 0.95 mV and 29 mu V sccm(-1), respectively, with power consumption less than 40 mW. The time-of-flight mode is found to have a wider detectable flow range compared with calorimetric mode, and the time of flight measured indicates a response time of the sensor in the millisecond range. The design and operation of a sensor with high sensitivity and large flow range are discussed. A key element of this discussion is the configuration of the array of heaters and gauges along the channel to obtain different sensitivities and extend the operational range. This means that the sensor can be tailored to different flow ranges.

  • 44.
    Palmer, Kristoffer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Lotfi, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Berglund, Martin
    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.
    Kratz, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A micromachined dual-axis beam steering actuator for use in a miniaturized optical space communication system2010In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 20, no 10, p. 105007-Article in journal (Refereed)
    Abstract [en]

    The design, fabrication and evaluation of an electrothermally actuated micromachined beam steering device for use in a free-space optical communication system intended for use on micro-and nanospacecraft in kilometer-sized formations are presented. SU-8 confined in v-grooves is heated to create bending movement in two orthogonal directions for two-axial steering with large static bending angles and low actuation voltages. Standard MEMS processing is used to fabricate the devices with square mirror side lengths of 1, 3.5 and 5 mm. In addition, a method to prevent thermal damage to SU-8 during deep reactive ion etching has been successfully developed. Characterization shows optical scan ranges larger than 40 degrees in both directions with the maximum driving voltage of 16 V corresponding to a total power consumption of 1.14 W. Infrared imaging is used to investigate thermal cross-talk between actuators for the two scanning directions. It is found that a silicon backbone on the joint backside is crucial for device performance. Differences from expected performance are believed to arise from the SU-8 curing process and excessive heating during fabrication. A finite element method simulation is used to find the eigenfrequencies of the structures, and these are in good agreement with the measured frequency response.

  • 45.
    Palmer, Kristoffer
    et al.
    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.
    Fabrication and evaluation of a free molecule micro-resistojet with thick silicon dioxide insulation and suspension2013In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 23, no 6, p. 065006-Article in journal (Refereed)
    Abstract [en]

    A silicon free molecule micro-resistojet (FMMR) with a thermally insulating suspension frame composed of silicon dioxide has been designed, fabricated and tested. The concept was developed to increase the efficiency of FMMRs, especially in silicon-based integrated systems. Fabrication of the thick insulating frame was performed through oxidation of high-aspect ratio silicon trenches. The thermal properties of the 1 cm(2) thruster were evaluated using an IR camera, and it was found that when the volume inside the frame is heated more than 200 degrees C using integrated nickel heaters, the temperature increase in the volume outside the frame is less than 50 degrees C. During operation in vacuum, the thrust range was calculated to be about 13-1070 mu N and the maximum specific impulse 54 s. At maximum thrust, and a power consumption of 1.6 W, the total efficiency of the thruster was 17%. Designs of more efficient and versatile systems are discussed.

  • 46.
    Palmer, Kristoffer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Vargas Catalan, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Lekholm, Ville
    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 exhausts from fabricated silicon micronozzles with rectangular and close to rotationally symmetric cross sections2013In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 23, no 10, p. 105001-Article in journal (Refereed)
    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.

  • 47.
    Persson, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Berglund, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology, Ångström Space Technology Centre (ÅSTC).
    Khaji, Zahra
    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 Def Univ, Div Mil Technol, Dept Mil Sci, Stockholm, Sweden.
    Söderberg, Johan
    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).
    Optogalvanic spectroscopy with microplasma sources – Current status and development towards lab on a chip2016In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 26, no 10, article id 104003Article in journal (Refereed)
    Abstract [en]

    Miniaturized optogalvanic spectroscopy (OGS) shows excellent prospects of becoming ahighly sensitive method for gas analysis in micro total analysis systems. Here, a status reporton the current development of microwave induced microplasma sources for OGS is presented,together with the first comparison of the sensitivity of the method to conventional single-passabsorption spectroscopy. The studied microplasma sources are stripline split-ring resonators(SSRRs), with typical ring radii between 3.5 and 6 mm and operation frequencies around2.6 GHz. A linear response (R2 = 0.9999), and a stability of more than 100 s are demonstratedwhen using the microplasma source as an optogalvanic detector. Additionally, saturationeffects at laser powers higher than 100 mW are observed, and the temporal response of theplasma to periodic laser perturbation with repletion rates between 20 Hz and 200 Hz arestudied. Finally, the potential of integrating additional functionality with the detector isdiscussed, with the particular focus on a pressure sensor and a miniaturized combustor toallow for studies of solid samples.

  • 48.
    Persson, Anders
    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.
    Thornell, Greger
    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.
    Etch-stop technique for patterning of tunnel junctions for a magnetic field sensor2011In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 21, no 4, p. 045014-045022Article in journal (Refereed)
    Abstract [en]

    Spin-dependent tunnelling devices, e. g. magnetic random access memories and highly sensitive tunnelling magnetoresistance (TMR) sensors, often consist of a large number of magnetic tunnel junctions (MTJs) of uniform quality over the whole device. The uniformity and yield of the fabrication of such a device are therefore very important. A major source of yield loss is the short-circuiting of junctions by redeposition of etch residues. This can be prevented by terminating of the etch in the typically 1 nm thick tunnelling barrier. Here, electron spectroscopy for chemical analysis for monitoring the etching semi-continuously is proposed. The fabrication scheme employs Ar ion milling for etching the MTJs, and photoelectron spectroscopy for analysing the composition of the etched surface in situ. Junctions etched either to or through the barrier were used for this. The quality of the etch stop was investigated using transmission electron microscopy (TEM), and it was confirmed that the etch could be stopped in the MgO barrier. The TEM imaging also showed clear signs of redeposition. Such redeposition was attributed to being partly caused by the reduction of the TMR ratio of the junctions etched through the barrier, which was only 15% as compared with 150% for junctions etched to the barrier. Also, the latter junctions exhibited 2.7 times less noise in the low-frequency regime, resulting in a 27 times improvement of the signal-to-noise ratio with the etch stop. The barrier also proved effective in protecting the bottom contact from oxidation during the capping and contacting of the junctions.

  • 49.
    Persson, Anders
    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.
    Nguyen, Hugo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Rapid prototyping of magnetic tunnel junctions with focused ion beam processes2010In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 20, no 5, p. 055039-Article in journal (Refereed)
    Abstract [en]

    Submicron sized Magnetic tunnel junctions (MTJs) are most often fabricated by time-consuming and expensive e-beam lithography. From a research and development perspective, a short lead time is one of the major concerns. Here, a rapid process scheme for fabrication of micrometer size MTJs with focused ion beam processes is presented. The magnetic properties of the fabricated junctions is investigated in terms of magnetic domain structure, tunnelling magnetoresistance (TMR) and coercivity, with extra attention to the effect of Ga implantation from the ion beam. In particular, the effect of the implantation on the minimum junction size and the magnetization of the sensing layer are studied. In the latter case, magnetic force microscopy and micromagnetic simulations, with the Object Oriented Micromagnetic Framework (OOMMF), are used to study the magnetization reversal. The fabricated junctions show considerable coercivity both along their hard and easy axes. Interestingly, the sensing layer exhibit two remanent states: one with a single and one with a double domain. The hard axis TMR loop has kinks at about ±20 mT which is attributed to a non-uniform lateral coercivity, where the rim of the junctions, which is subjected to Ga implantation from the flank of the ion beam, is more coercive than the unirradiated centre. The width of the coercive rim is estimated to 160 nm from the hard axis TMR loop. The easy axis TMR loop shows more coercivity than an unirradiated junction and, this too, is found to stem from the coercive rim, as seen from the simulations. It is concluded that the process scheme has three major advantages. Firstly, it has a high lateral and depth resolution – the depth resolution is enhanced by end point detection – and is capable of making junctions of sizes down towards the limit set by the width of the irradiated rim. Secondly, the most delicate process steps are preformed in unbroken vacuum enabling the use of materials prone to forming oxides in the MTJ film stack. Thirdly, the scheme is both uncomplicated and quick and makes it possible to go from design to characterization in the order of hours.

  • 50. Rosengren, L
    et al.
    Bäcklund, Ylva
    Sjöström, T
    Hök, Bertil
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Svedbergh, Björn
    A system for wireless intraocular pressure measurements using a silicon micromachined sensor1992In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 2, p. 202-204Article in journal (Refereed)
12 1 - 50 of 72
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf