Robo-Coverstitch: Coverstitched Auxetic Shape Memory Actuators For Soft Wearable Devices

As wearable technologies proliferate there is a growing need for compact, easy-to-produce textile-based mechanical actuators. This paper presents a novel coverstitched auxetic actuator using shape memory alloys (SMAs) -- which we call the Robo-coverstitch – that can be easily sewn onto fabrics using an industrial coverstitch machine. Multiple Robo-coverstitch samples were manufactured and tested to characterize their force vs. strain properties. The samples were actuated in both the length- and width-wise direction between 0-15% strain at constant electrical current (0.4A). The actuators produced increased force in both length- and width-wise directions when actuated (i.e., auxetic actuation behavior), and these active forces increased with actuator strain. The Robo-coverstitch offers an unobtrusive mechanical actuation solution that can be readily deployed into commercial garments.