A New 10-mg SMA-Based Fast Bimorph Actuator for Microrobotics

We present a new millimeter-scale bimorph ac- tuator for microrobotic applications, driven by feedforward controlled shape-memory alloy (SMA) wires. The device weighs 10 mg, measures 14 mm in length, and occupies a volume of 4.8 mm3, which makes it the lightest and smallest fully func- tional SMA-based bimorph actuator for microrobotics devel- oped to date. The experimentally measured operational band- width is on the order of 20 Hz, and the unimorph and bimorph maximum low-frequency displacement outputs are on the order of 3.5 and 7 mm, respectively. To test and demonstrate the functionality and suitability of the actuator for microrobotics, we developed the Fish-&-Ribbon–Inspired Small Swimming Har- monic roBot (FRISSHBot). Loosely inspired by carangiformes, the FRISSHBot leverages fluid-structure interaction (FSI) phe- nomena to propel itself forward, weighs 30 mg, measures 34 mm in length, operates at frequencies of up to 4 Hz, and swims at speeds of up to 3.06 mm · s−1 (0.09 Bl · s−1). This robot is the lightest and smallest swimmer with onboard actuation developed to date.