A New 1-mg Fast Unimorph SMA-Based Actuator for Microrobotics

We present a new unimorph actuator for microrobotics, which is driven by thin shape-memory alloy (SMA) wires. Using a passive-capillary-alignment technique and existing SMA-microsystem fabrication methods, we developed an actuator that is 7mm long, has a volume of 0.45mm(3), weighs 0.96 mg, and can achieve operation frequencies of up to 40 Hz as well as lift 155 times its own weight. To demonstrate the capabilities of the proposed actuator, we created an 8-mg crawler, the MiniBug, and a bioinspired 56-mg controllable water-surface-tension crawler, the WaterStrider. The MiniBug is 8.5mm long, can locomote at speeds as high as 0.76 BL/s (body-lengths per second), and is the lightest fully-functional crawling microrobot of its type ever created. The WaterStrider is 22mm long, and can locomote at speeds of up to 0.28 BL/s as well as execute turning maneuvers at angular rates on the order of 0.144 rad/s. The WaterStrider is the lightest controllable SMA-driven water-surface-tension crawler developed to date.