Recent advances for phase-transition materials for actuators

Mechanical actuators, which convert external stimuli to motion, play a significant role in medical devices, automobiles, aircrafts, and robots. With their associated advantages of large shape change, high force, and high efficiency, phase transitions are among the most important driving forces in actuation. There are many phase-transition materials suitable for actuators, and many of them find applications in the real world. In this Tutorial, we review some typical phase-transition driving materials for actuators, including shape memory alloys, piezoelectric ceramics, vanadium dioxide, liquid crystal elastomers, hydrogels, shape memory polymers, and paraffin wax. The phase-transition mechanisms of the materials are introduced, and the design principles and related applications of the associated actuators are discussed.