Restructurable materials for soft actuators

Soft actuators are widely employed in soft robotics, wearable sensors, and human-machine interfaces. Being assembled upon stimuli-responsive materials, the state-of-the-art soft actuators are presumed to not only perform complex robotic tasks, but also to be repaired after mechanical damage or long-term usage. Although meeting these requirements could be a challenge for actuators based on traditional thermosetting/thermoplastic elastomers, soft actuators built on restructurable materials can be an alternative, since both the actuation and healing functions rely on the stimuli-responsive structural rearrangement of these materials. Specifically, self-healing polymers have been demonstrated to be promising candidates for assembling restructurable actuators. This paper summarizes the reprogramming pathways of stimuli-responsive actuators; reviews the design strategies for constructing reprogrammable mono-layered actuators with the various types of dynamic polymer networks, especially with self-healing polymers; the design strategies for assembling bi- or multi-layered actuators with tailored interfacial structure, and proposes the outlook for the development of restructurable actuators.