A. P. Jardine, Shape Change Technologies LLC, Thousand Oaks, CA
Thin film TiNi has been investigated by a variety of researchers over the past 10 years, however the key of a manufacturable process that can generate consistent yields over the wafer and from batch to batch is of importance. A sputtering technique that can generate consistent yields over the surface of a silicon wafer, as well as generating good batch-to-batch consistency, is now being investigated. After the initial thin film processing, fenestration techniques of the thin films, either in martensitic or super elastic states, has been developed. The mechanical properties of the thin film are demonstrated to be dependent on both composition and processing. Finally, the use of solid thin films as actuators for pumps, such as for drug delivery systems, and as a stent covering, will be discussed.
Summary: Thin Film shape memory alloys (SMA) are promising actuator materials for a wide range of micro-systems technology especially biomedical applications Shape memory materials, such as NiTi, produce larger displacements/strains and larger forces/stresses per unit of material than other solid state actuators such as piezoelectric and magnetostrictive materials. In the thin film form, shape memory alloys also have substantially larger frequency response than bulk shape memory material due to the thin films larger surface area to volume ratio. An added advantage of NiTi shape memory alloy is the material is biocompatibility as demonstrated in the large use of NiTi stents and other biomedical devices. These advantages suggest a large number of micro-systems biomedical technologies exist for NiTi shape memory alloys, however fabricating the film and introducing it into a specific device has proven difficult.
