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Microsystems for Harsh Environments
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.ORCID iD: 0000-0003-2445-4624
2015 (English)Doctoral 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.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. , 50 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1263
Keyword [en]
Microsystems, harsh environments, high pressures, high temperatures, supercritical microfluidics
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
URN: urn:nbn:se:uu:diva-253558ISBN: 978-91-554-9272-4 (print)OAI: oai:DiVA.org:uu-253558DiVA: diva2:815222
Public defence
2015-09-11, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2015-08-19 Created: 2015-05-29 Last updated: 2015-09-07
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
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2010 (English)In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 19, no 6, 1462-1469 p.Article 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.

Keyword
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, 075010- p.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.

Keyword
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.

Keyword
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
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2015 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 25, no 10, 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. 

Keyword
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: 2017-12-04Bibliographically 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, 649-656 p.Article 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. 

Keyword
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: 2017-12-04Bibliographically 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
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2015 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 25, no 9, 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. 

Keyword
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: 2017-12-04Bibliographically 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

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