Rapid Prototyping of Microactuators by Integrating 3D Printed Polymeric Structures with NiTi Thin Film

This work demonstrates the first sputtered thin-film nickel-titanium (NiTi) shape-memory alloy (SMA) actuators combined with direct 3D printing of polymeric structures. Resulting actuators are fast to prototype, reliable and stable (up to 5000 cycles), and can utilize complex geometries challenging to achieve with conventional MEMS microfabrication. The actuator design uses 3D printed polymer as the passive layer in unimorph actuators, adding significant versatility to the actuator design. An actuator designed for high force-displacement was fabricated with a $15\ \ \mu \mathrm{m}$ thick polymer layer and characterized by applying currents up to 18 ma (7.3 mW, producing ∼156°C) resulting in a maximum displacement of $3.3\ \mu \mathrm{m}$ and ∼0.9 mN blocking force. Dynamic operation with falling/rising times of 20.1 ms/9.8 ms and 33.5 Hz maximum operation frequency was also demonstrated.