# Soft Robots with Plant‐Inspired Gravitropism Based on Fluidic Liquid Metal

## TL;DR

Researchers created soft robots inspired by plant gravitropism using liquid metal, enabling gravity-responsive movement without electronics.

## Contribution

A novel gravity-responsive soft actuator using fluidic liquid metal and thermoresponsive materials is introduced.

## Key findings

- A gravity-adaptive soft actuator was developed using liquid metal and thermoresponsive liquid crystal elastomer.
- A gravity-interactive gripper with controllable grasping and releasing was demonstrated.
- Self-regulated oscillation motion was achieved using a monostable tape spring interface.

## Abstract

Plants can autonomously adjust their growth direction based on the gravitropic response to maximize energy acquisition, despite lacking nerves and muscles. Endowing soft robots with gravitropism may facilitate the development of self‐regulating systems free of electronics, but remains elusive. Herein, acceleration‐regulated soft actuators are described that can respond to the gravitational field by leveraging the unique fluidity of liquid metal in its self‐limiting oxide skin. The soft actuator is obtained by magnetic printing of the fluidic liquid metal heater circuit on a thermoresponsive liquid crystal elastomer. The Joule heat of the liquid metal circuit with gravity‐regulated resistance can be programmed by changing the actuator's pose to induce the flow of liquid metal. The actuator can autonomously adjust its bending degree by the dynamic interaction between its thermomechanical response and gravity. A gravity‐interactive soft gripper is also created with controllable grasping and releasing by rotating the actuator. Moreover, it is demonstrated that self‐regulated oscillation motion can be achieved by interfacing the actuator with a monostable tape spring, allowing the electronics‐free control of a bionic walker. This work paves the avenue for the development of liquid metal‐based reconfigurable electronics and electronics‐free soft robots that can perceive gravity or acceleration.

Gravity‐responsive soft actuators are created using liquid metal and thermoresponsive liquid crystal elastomer. The Joule heat of the liquid metal circuit with gravity‐regulated resistance can be programmed by changing the actuator's pose to induce the flow of liquid metal. A gravity‐adaptive actuator, a gravity‐interactive gripper, and a self‐regulated snapping oscillator or walker are also demonstrated.