Fabrication of TiNi shape memory micropump

We have developed a shape memory alloy (SMA) actuated micropump as a compon ent for use in micro analysis or micro dosage systems. In this paper, we wi ll discuss the fabrication process and dynamic actuation properties of an S MA actuator, as well as the first result of pumping properties of a complet ed SMA micropump. TiNi thin film of about 6 mum in thickness was deposited onto a Si wafer with a square recess on its reverse side, and memorized an initial flat shape. The TiNi thin film and a Pyrex glass cap with a square recess were then anodically bonded together in a vacuum to form a chamber t o which a bias pressure was to be applied to deform the TiNi thin film. Aft er removing the remaining Si layer beneath the TiNi thin film by RTE in SF6 plasma, a shape memory actuator of 5 mm square in size was completed. A Si check valve structure was also fabricated through a process of anisotropic etching and fusion bonding and was assembled with the actuator. The fabric ated micropump with a size of 10 mm x 20 mm x 1.4 mm was driven by thermal cycles of resistive heating and air-cooling under bias pressure which was a pplied by a nitrogen gas flow. The completed SMA micropump proved to give a flow rate of 0.4 mul per cycle at a bias pressure of 100 kPa. (C) 2001 Els evier Science B.V. All rights reserved.