Low electric field-driven and fast-moving relaxor ferroelectric soft robots

Abstract

Bioinspired soft robots hold great potential to perform tasks in unstructured terrains. Ferroelectric polymers are highly valued in soft robots for their flexibility, lightweight, and electrically controllable deformation. However, achieving large strains in ferroelectric polymers typically requires high driving voltages, posing a significant challenge for practical applications. In this study, we investigate the role of crystalline domain size in enhancing the electrostrain performance of the relaxor ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene-fluorinated alkynes) (P(VDF-TrFE-CFE-FA)). Leveraging its remarkable inverse piezoelectric coefficient (|d₃₃*| = 701 pm V⁻¹), we demonstrate that the planar films exhibit a five times larger bending angle than that of commercial PVDF films at low electric fields. Based on this material, we design a petal-structured soft robot that achieves a curvature of up to 4.5 cm⁻¹ at a DC electric field of 30 V μm⁻¹. When integrated into a bipedal soft robot, it manifests outstanding electrostrain performance, achieving rapid locomotion of ~19 body lengths per second (BL s⁻¹) at 10 V μm⁻¹ (560 Hz). Moreover, the developed robot demonstrates remarkable abilities in climbing slopes and carrying heavy loads. These findings open new avenues for developing low-voltage-driven soft robots with significant promise for practical applications.