Cory R Knick and Christopher J Morris
Posters-Accepted Abstracts: J Material Sci Eng
In this work we discuss the design and fabrication of a cantilever that may be actuated by utilizing the martensite to austenite phase transformation of a sputtered thin film of equiatomicNiTi shape memory alloy (SMA). The cantilever devices were fabricated on a silicon wafer using standard micro fabrication techniques, and may therefore be applicable to Micro-Electro- Mechanical Systems (MEMS) switch or actuator applications. This paper details the development of a co-sputtering process to yield a SMA film with controllable composition of Ni50Ti50 and transformation temperature around 60°C. Shape memory effects were characterized using Differential Scanning Calorimetry (DSC), for which we demonstrated martensite-austenite phase change at 57°C for 1-3 μm films, annealed at 600°C. We used wafer stress versus temperature measurements as additional confirmation for the repeatable measurement of reversible phase transformation peaking at 73°C upon heating. Up to 62 MPa was available for actuation during the thermally induced phase change. After exploring multiple approaches to a frontside wafer release process, we were successful in patterning and fabricating freestanding NiTi cantilevers that exhibited out of plane curling upon heating.
Journal of Material Sciences & Engineering received 3043 citations as per Google Scholar report