Shape Memory Thin Film for Blood Vessel Holding Actuator of Thrombus Detector

For the purpose of an application for a blood vessel holding actuator of thrombus detector, evaporation technique and film properties of TiNiCu ternary shape memory alloy (SMA) thin film was studied. The SMA thin film was formed on a sacrificial Cu substrate by using a flash evaporation technique, with which very small TiNiCu alloy pellets were evaporated repeatedly. With this evaporation technique, phase transformation temperature of the deposited thin film can be controlled by deposition timing after the each pellet starts to vaporize. When the interval time before the deposition was 0s, the deposited thin film became a super elastic alloy (SEA), which starts to deform below the human body temperature of 37°C. On the other hand, when the interval time was 1s or longer, the deposited thin film shows a shape recovery temperature of about 60°C. Fracture strength of the thin film was obtained at least 170MPa, that corresponds to a fracture force of 570mN for holding actuator of 0.6mm in width and 6µm in thickness. Although the SEA film was fragile, the SMA film at the interval time of 5s was flexible enough to be bendable to small radius of 0.15mm.