In this work, we present a thin-film shape memory alloy microactuator with a magnetic spring. This novel actuator design utilizes two permanent magnets and 3D-printed magnet holders to effectively apply a tensile strain on the NiTi thin-film. This actuator is expected to generate 8.7 mN of blocking force, and a free displacement of 30 µm is experimentally characterized. The actuator leverages bare NiTi film (∼ 1 µm thick) for actuation, enabling a high actuator bandwidth up to 50 Hz. A comprehensive analytical model is also studied, which was then validated by comparing to the experimental results. A launcher mechanism was designed and integrated with the NiTi actuator, and this mechanism was used to launch a microscale projectile (a salt grain) thereby demonstrating the relative high power actuation achievable with thin-film NiTi.

Creating microscale actuated mechanisms in 3D space is extremely challenging due to limitations in microfabrication processes. In this work, we present a 3D-printed adaptive microgripper that is driven by thin-film NiTi microactuators with 3D-printed linkage mechanisms. The microgripper's fingers are passively adaptive so that the microgripper can provide conformal gripping on 3D objects. The microgripper can move its fingers by$\mathbf{225}\ \boldsymbol{\mu} \mathbf{m}$and apply a blocking force of$\mathbf{30}\ \boldsymbol{\mu} \mathbf{N}$per one finger when 20 mA was applied to the NiTi actuators. The microgripper was also integrated onto a printed circuit board with a current regulating circuit and a 9 V battery. Since the NiTi actuator requires a low voltage for actuation, the microgripper could be integrated with simple and affordable electronics. The fully integrated microgripper system was demonstrated playing with a shape sorting box at the microscale for the first time.