A bidirectional shape memory alloy folding actuator

This paper presents a low-profile bidirectional folding actuator based on annealed shape memory alloy sheets applicable for meso-and microscale systems. Despite the advantages of shape memory alloys-high strain, silent operation, and mechanical simplicity-their application is often limited to unidirectional operation. We present a bidirectional folding actuator that produces two opposing 180 degrees motions. A laser-patterned nickel alloy (Inconel 600) heater localizes actuation to the folding sections. The actuator has a thin (<1 mm) profile, making it appropriate for use in robotic origami. Various design parameters and fabrication variants are described and experimentally explored in the actuator prototype.