Shape Memory Alloy (SMA) Actuators: The Role of Material, Form, and Scaling Effects.

Shape memory alloys (SMAs) are smart materials that are widely used to create intelligent devices because of their high energy density, actuation strain, and biocompatibility characteristics. Given their unique properties, SMAs have been found to have significant potential for implementation in many emerging applications in mobile robots, robotic hands, wearable devices, aerospace/automotive components, and biomedical devices. In this review, we summarize the state-of-the-art of thermal and magnetic SMA actuators in terms of their constituent materials, form, and scaling effects, including their surface treatments and functionalities. We also analyze the motion performance of various SMA architectures (wires, springs, smart soft composites, and knitted/woven actuators). Based on our assessment, we emphasize current challenges of SMAs that need to be addressed for their practical application. Finally, we suggest how to advance SMAs by synergistically considering the effects of material, form, and scale. This article is protected by copyright. All rights reserved.