Earthworm‐Inspired Multi‐Material, Adaptive Strain‐Limiting, Hybrid Actuators for Soft Robots

Abstract

This research presents a new class of versatile multi‐material hybrid actuators (MASH actuators), powered by pneumatics and electrostatic adhesion (EA)‐based adaptive strain‐limiting layers. Soft pneumatic actuators with strain‐limiting layers as the mainstream actuation for soft robotics have been developed for decades. However, due to their permanent strain‐limiting layers, those actuators possess fewer motion patterns. Inspired by the longitudinal muscles of the earthworm, a concept of an adaptive strain‐limiting layer with the ability to vary its length, stiffness, and position is presented. By integrating two flexible EA brakes into a soft pneumatic actuator as adaptive strain‐limiting layers, the actuator can achieve multiple motion patterns including extension, contraction, and bilateral bending, with permutations among these motions. The EA‐based strain‐limiting layer can increase the original actuator length by up to 86%, and the baseline actuator stiffness by up to 605%. To demonstrate its potential in locomotion and manipulation, an earthworm‐inspired crawling robot possessing great terrain adaptability and a versatile soft robotic gripper based on this hybrid actuator concept are developed.