Bioinspired soft caterpillar robot with ultra-stretchable bionic sensors based on functional liquid metal

Abstract

Soft robots have significant advantages in terms of flexibility and adaptability, leading to potential applications in the bionics field. Inspired by the caterpillars in nature, this work proposed a soft caterpillar robot (SCR) by integrating two types of ultra-stretchable bionic sensors on a dual air-chamber pneumatic network structure. In order to realize self-powered tactile sensing, four triboelectric nanogenerator tactile sensors (TTSs) based on functional liquid metal (FLM) with thorny-structured bionic whiskers are developed and attached on the SCR. Meanwhile, two ultra-stretchable resistive strain sensors (RSSs) by using FLM are covered as the bionic skin to sense self-body deformation of the SCR. The TTS has a fast response time of 0.03 s and a minimum perception of 0.05 kPa, which can be very sensitive to the unknown stimulus of various materials. The RSS with a relatively high sensitivity of 2.94 and small hysteresis of 1.42% possess the ultra-stretchable ability of 180% strain, which helps to adapt and adjust its own body bending and crawling. The biological perception capabilities of the SCR play a crucial role in mimicking bionic actions and response in an unknown environment, such as escaping from unexpected attacks as well as adaptive crawling through an unknown tunnel environment. Soft robots have significant advantages in terms of flexibility and adaptability, leading to potential applications in the bionics field. Inspired by the caterpillars in nature, this work proposed a soft caterpillar robot (SCR) by integrating two types of ultra-stretchable bionic sensors on a dual air-chambers of pneumatic network structure. In order to sense self-body deformation of the SCR, two ultra-stretchable resistive strain sensors (RSSs) by using functional liquid metal (FLM) are covered as the bionic skin. Meanwhile, four triboelectric tactile sensors (TTSs) based on FLM with thorny-structured bionic whiskers are developed and attached on the head, tail and body of the soft caterpillar, respectively, to realize self-powered tactile sensing. The biological perception capabilities of the SCR play a crucial role to mimic bionic actions and response in an unknown environment, such as escaping from unexpected attacks as well as adaptive crawling through an unknown tunnel environment. • The ultra-stretchable bionic sensors based on FLM were integrated on a SCR to realize bionic sensing. • The TTS was sensitive to the unknown stimulus of various materials. The RSS was sensitive to the bending of SCR. • Closed-loop control enabled SCR to achieve intelligent sensing and automatic motion.