NiTi shape memory alloy thin film sensor micro-array for detection of infrared radiation

An uncooled imaging sensor design that utilizes the thermo-mechanical properties of thin film NiTi shape memory alloys (SMAs) for detecting far infrared (IR) radiation was fabricated. The NiTi SMA thin films were prepared by dc magnetron sputtering deposition and made into two-dimensional cantilever micro-arrays by photolithographic techniques. The thickness and the composition of the film were approximately 5 μm and 49.75 at.% Ti, respectively. After the crystallization and aging heat treatments, the NiTi SMA thin films exhibited phase transition at near room temperatures which corresponds to the R-phase transition. Upon the absorption of IR radiation, NiTi SMA thin film was heated up leading to reverse R-phase transition. Illumination of the micro-array can increase the temperature locally and cause bending of the two-way shape memory (TWSM) thin film.