Thin film shape memory microvalves with adjustable operation temperature

Gas microvalves of about 3 x 3 x 5 mm(3) size are presented, which are actu ated by a microdevice of shape memory alloy (SMA) thin film with stress-opt imized shape. By variation of the chemical composition of the material syst em Ti-Ni-Pd, the phase transformation temperatures have been adjusted in a range below 405 K in order to design the operation temperature of the valve s. The main fabrication technologies were magnetron sputtering and electrol ytic photoetching of the thin films and hybrid integration of the valve com ponents. The SMA microvalves work in a normally open mode and allow control of pressure differences below 2500 hPa at gas flows below 360 standard ccm (sccm). (C) 2000 Elsevier Science S.A. All rights reserved.