Progress in the Field of Water- and/or Temperature-Triggered Polymer Actuators

Water- and/or temperature-triggered polymer actuators have great potential in robotics, microfabrication and micromanipulation, cell culture, artificial scaffolds, muscles, and motors. In the past few years, a large amount of work has been carried out, and several innovative concepts have been proposed to address challenges such as actuation with large-scale displacement in a very short time, actuation of large-sized samples, complex 3D shaping, directional control, multiresponsive actuation, and strong actuators. Herein, the progress made in the field of actuators triggered by water, temperature, and a combination of both is presented, emphasizing the new concepts of fast and direction-controlled actuation, the corresponding mechanisms, the associated challenges, and future tasks and perspectives.