High-Performance Multiresponsive Bilayer Actuators Based on Micro-/Nanostructured Polypyrrole for Robust Smart Devices

Bioinspired soft actuators have great application potentials in many fields. However, so far, it has remained a great challenge to realize high-performance actuators with a low-cost manufacturability, good mechanical stability, excellent multiresponsive ability, large deformation capability, and fast movement. Here, we report a high-performance multiresponsive bilayer actuator, in which a polypyrrole (PPy) layer is deposited on a polyethylene glycol terephthalate (PET) substrate via a simple aqueous chemical oxidation polymerization with in situ formation of PPy hierarchical micro-/nanostructures. The resultant robust PPy/PET bilayer actuator has outstanding humidity/light/electricity/thermal responses coupled with a large deformation. These actuating behaviors originate from the stimulus-triggered synergistic deformations of the bilayer because of their large thermal expansion mismatch and the coupling effect of the hygroscopic ability of micro-/nanostructured PPy with its photothermal effect and conductivity. Taking advantage of the multiresponsive characteristics combined with unexploited laser-engraved geometries of PPy, we realize diverse reversible complex deformations between two- and three-dimensional (2D and 3D) configurations in a controlled manner. More importantly, we develop the applications of the PPy/PET bilayer actuator as a power-free humidity self-driven hygrometer and smart humidity-tunable clothing. Meanwhile, we realize temperature-gradient-driven unprecedented ultrafast rolling of the actuator, in addition to light-induced crawling. As demonstrated, the multiresponsive PPy-based bilayer actuators may find broad applications such as artificial muscles, soft microrobots, and so on.