Soft Swimming Robot Driven by Electroosmotic Propulsion with Silent and Programmable Locomotion

Abstract

Soft robotic systems operating in liquid environments require propulsion mechanisms that combine structural compliance, stable thrust generation, and low hydrodynamic disturbance. However, conventional mechanical propulsion methods often rely on moving components that generate acoustic noise, pulsatile flow, and turbulence, limiting their use in delicate fluidic environments. Here, we present a centimeter-scale fully soft swimming robot powered by an integrated electroosmotic microchannel propulsion module. Each compact module, with a volume of 0.04 cm3, incorporates 120 parallel microchannels and liquid metal electrodes within a flexible elastomeric body, directly converting electrokinetic transport into continuous fluid thrust without mechanical moving parts. The module maintains consistent thrust output under substantial bending deformation, demonstrating mechanical resilience and operational reliability within a soft robotic body. As a functional demonstration, the robot achieves a swimming speed of 2.85 body lengths per second and a turning speed of 62° s–1 using a single module, while consuming only 60 mW of power. It also exhibits a high thrust capacity, pushing objects up to 13 times its own weight. A dual-module configuration enables programmable locomotion, including in-place rotation and rapid directional switching. The robot further demonstrates safe interaction with live aquatic organisms, highlighting its potential for low-disturbance operation in sensitive liquid environments. These results establish embedded electroosmotic microchannel propulsion as a materials-enabled strategy for soft actuation, microfluidic propulsion, and bioinspired robotic systems.