Fabrication of TiNi shape memory micropump

Abstract

We have developed a shape memory alloy (SMA) actuated micropump as a component for use in micro analysis or micro dosage systems. In this paper, we will discuss the fabrication process and dynamic actuation properties of an SMA actuator, as well as the first result of pumping properties of a completed SMA micropump. TiNi thin film of about 6 μm 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 to which a bias pressure was to be applied to deform the TiNi thin film. After removing the remaining Si layer beneath the TiNi thin film by RIE in SF 6 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 fabricated micropump with a size of 10 mm×20 mm×1.4 mm was driven by thermal cycles of resistive heating and air-cooling under bias pressure which was applied by a nitrogen gas flow. The completed SMA micropump proved to give a flow rate of 0.4 μl per cycle at a bias pressure of 100 kPa.