Abstract

Mechanical instabilities are emerging as novel actuation mechanisms for the design of biomimetic soft robots and smart structures. The present study shows that by coupling buckling-driven elastomeric auxetic modules actuated by a negative air-pressure, a novel metamaterial-based caterpillar can be designed-the Metarpillar. Following a detailed analysis of the caterpillar's locomotion, we were able to mimic both its crawling movement and locomotion by using the unique isometric compression of the modules and properly programing the anterograde modular peristaltic contractions. The bioinspired locomotion of the Metarpillar uses the bending triggered by the buckling-driven module contraction to control the friction through a dynamic anchoring between the soft robot and the surface, which is the main mechanism for locomotion in caterpillars and other crawling organisms. Thus, the Metarpillar not only mimics the locomotion of the caterpillar but also displays dynamic similarity and equivalent, or even faster, speeds. Our approach based on metamaterial buckling actuator units opens up a novel strategy for biomimetic soft robotic locomotion that can be extended beyond caterpillars. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).