As it turns out, certain metal materials undergo shape changes when heated, and can reform into their original shape upon cooling. Known as the shape-memory effect, this recently-discovered phenomena has already been prototyped in automotive, aerospace, and biomedical applications.

Here, we describe how the shape-memory effect can be used to construct an actuator for biomimetic robots. Known as the shape-memory allow actuator (SMA), it is distinct in taking advantage of changes at the molecular level to generate a macroscopic contraction.

Left: Our SMA design in action, March 2021