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 are found to have significant potential for implementation in many emerging applications in mobile robots, robotic hands, wearable devices, aerospace/automotive components, and biomedical devices. Here, the state-of-the-art of thermal and magnetic SMA actuators in terms of their constituent materials, form, and scaling effects are summarized, including their surface treatments and functionalities. The motion performance of various SMA architectures (wires, springs, smart soft composites, and knitted/woven actuators) is also analyzed. Based on the assessment, current challenges of SMAs that need to be addressed for their practical application are emphasized. Finally, how to advance SMAs by synergistically considering the effects of material, form, and scale is suggested.

In article number 1606580, Min-Woo Han and Sung-Hoon Ahn report soft morphing structures, in which loop-linked structures made from thermally responsive fibers allow the creation of three-dimensional morphologies, including flowers. Based on the design methodology of loop patterning, the proposed morphing structures enable three-dimensional volumetric transformation as well as bending, twisting, and torsional deformation, through functional fiber actuation.