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SMA Microvalves for Very Large Gas Flow Control Manufactured Using Wafer-Level Eutectic Bonding
KTH, School of Electrical Engineering (EES), Microsystem Technology.
KTH, School of Electrical Engineering (EES), Microsystem Technology.ORCID iD: 0000-0001-9552-4234
KTH, School of Electrical Engineering (EES), Microsystem Technology.ORCID iD: 0000-0001-8248-6670
2012 (English)In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, Vol. 59, no 12, 4895-4906 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a novel gas microvalve design concept, in which a flow control gate is opened by a pneumatic pressure and closed by a shape memory alloy actuator, allowing large flow control. Two different design variations were fabricated using a novel wafer-level Au-Si eutectic bonding process for TiNi to silicon integration. The resulting microvalves demonstrate a record pneumatic performance per footprint area; a microvalve with a footprint of only 1 x 3.3 mm(2) successfully controls a flow difference of 3100 sccm at a pressure drop of 70 kPa using a power of 0.35 W.

Place, publisher, year, edition, pages
2012. Vol. 59, no 12, 4895-4906 p.
Keyword [en]
Eutectic bonding, Microvalve, Shape Memory Alloy, Wafer-scale integration
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-47632DOI: 10.1109/TIE.2011.2173892ISI: 000306142000040ScopusID: 2-s2.0-84863768457OAI: diva2:455837
EU, European Research Council, 267528
QC 20120806Available from: 2011-11-11 Created: 2011-11-11 Last updated: 2012-08-06Bibliographically approved
In thesis
1. Heterogeneous Integration of Shape Memory Alloysfor High-Performance Microvalves
Open this publication in new window or tab >>Heterogeneous Integration of Shape Memory Alloysfor High-Performance Microvalves
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents methods for fabricating MicroElectroMechanical System (MEMS) actuators and high-flow gas microvalves using wafer-level integration of Shape Memory Alloys (SMAs) in the form of wires and sheets.

The work output per volume of SMA actuators exceeds that of other microactuation mechanisms, such as electrostatic, magnetic and piezoelectric actuation, by more than an order of magnitude, making SMA actuators highly promising for applications requiring high forces and large displacements. The use of SMAs in MEMS has so far been limited, partially due to a lack of cost efficient and reliable wafer-level integration approaches. This thesis presents new methods for wafer-level integration of nickel-titanium SMA sheets and wires. For SMA sheets, a technique for the integration of patterned SMA sheets to silicon wafers using gold-silicon eutectic bonding is demonstrated. A method for selective release of gold-silicon eutectically bonded microstructures by localized electrochemical etching, is also presented. For SMA wires, alignment and placement of NiTi wires is demonstrated forboth a manual approach, using specially built wire frame tools, and a semiautomatic approach, using a commercially available wire bonder. Methods for fixing wires to wafers using either polymers, nickel electroplating or mechanical silicon clamps are also shown. Nickel electroplating offers the most promising permanent fixing technique, since both a strong mechanical and good electrical connection to the wire is achieved during the same process step. Resistively heated microactuators are also fabricated by integrating prestrained SMA wires onto silicon cantilevers. These microactuators exhibit displacements that are among the highest yet reported. The actuators also feature a relatively low power consumption and high reliability during longterm cycling.

New designs for gas microvalves are presented and valves using both SMA sheets and SMA wires for actuation are fabricated. The SMA-sheet microvalve exhibits a pneumatic performance per footprint area, three times higher than that of previous microvalves. The SMA-wire-actuated microvalve also allows control of high gas flows and in addition, offers benefits of lowvoltage actuation and low overall power consumption.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. viii, 79 p.
Trita-EE, ISSN 1653-5146 ; 2012:014
Microelectromechanical systems, MEMS, silicon, wafer-level, integration, heterogeneous integration, wafer bonding, Au-Si, eutectic bonding, release etching, electrochemical etching, microvalves, microactuators, shape memory alloy, SMA, NiTinol, TiNi, NiTi, cold-state reset, bias spring, gate valves, wire bonding
National Category
Engineering and Technology
urn:nbn:se:kth:diva-94088 (URN)978-91-7501-304-6 (ISBN)
Public defence
2012-06-01, sal E3, Osquarsbacke 14, KTH, Stockholm, 10:00 (English)
QC 20120514Available from: 2012-05-14 Created: 2012-05-07 Last updated: 2012-05-14Bibliographically approved

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Gradin, HenrikBraun, StefanStemme, GöranWijngaart, Wouter van der
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