Micropump with TiNi Shape Memory Diaphragm Actuator

Abstract

We fabricated a micropump with a circular actuator of shape memory alloy (SMA) diaphragm. The actuator consisted of a TiNi diaphragm of 5mm in diameter and 6μm in thickness, and a glass cap. This was fabricated through a process sequence of Si isotropic etching, flash evaporation of the TiNi thin film, annealing for shape memorization, removing of the undesired Si layer by reactive ion etching, and anodic bonding of the glass cap to the diaphragm structure. The fabricated actuator gave about 90μm displacement at the center of the diaphragm under a bias pressure of 200kPa. The SMA micropump, which was completed by gluing the Si check valve with a cantilever valve flap to the actuator, gave a pumping rate of 3-15μL/min at heating energy of 3-9 J under a bias pressure of 200kPa and at zero back pressure. Experimental data indicate that the fabricated SMA diaphragm is acceptable as an actuator of a micropump, while the fabricated valve structure is insufficient as a check valve for high pressure application due to a leak problem.