An Amphibious Untethered Inchworm Soft Robot for Fast Crawling Locomotion

TL;DR

This work tackles the challenge of deploying soft robots in real-world, multitask environments by introducing a fully untethered, magnetically actuated soft robot with an integrated onboard control board and camera. The design leverages a curved bilayer elastomer shell embedded with permanent magnets and externally controlled magnetic coils, enabling fast terrestrial crawling ($ ext{up to }$ $3.74$ cm/s) and water-surface swimming ($ ext{up to }$ $0.82$ cm/s), while also supporting steering and payload transport. Key contributions include the fabrication of a compact curved soft body, magnetic field actuation with explicit field strengths and forces, a lightweight onboard electronics package, and a gait framework that supports both ground and aquatic locomotion. Experimental results validate multimodal performance, demonstrating robust operation across flat, inclined, and aquatic environments, and highlighting the practical potential of electromagnetic actuation for untethered soft robotics.

Abstract

Untethered soft robots are essential for advancing the real-world deployment of soft robotic systems in diverse and multitasking environments. Inspired by soft-bodied inchworm, we present a fully untethered soft robot with a curved, flexible structure actuated by magnetic forces. The robot has a total mass of 102.63 g and demonstrates multimodal locomotion, achieving a maximum walking speed of 3.74 cm/s and a swimming speed of 0.82 cm/s. A compact and lightweight onboard control circuit enables wireless command transmission, while an integrated camera provides environmental perception. Through structural optimization and system-level integration, the robot successfully performs walking, steering, swimming, and payload transport without reliance on external infrastructure. The robot's dynamic performance and locomotion capabilities are systematically validated through experimental characterization.

Figures (13)

• Figure 1: Bioinspiration of the proposed robot. (a) An inchworm in crawling motion zhang2024. (b) The developed untethered soft robot, designed with a curved flexible body to mimic inchworm's crawling locomotion.
• Figure 2: Components of the shape-morphing magnetic soft robot.
• Figure 3: Fabrication of the soft magnetic robot. Fabrication schematic: (a) elastomer cured on pre-stretched layer with magnets on front and back legs. (b) Soft body with attached shoes. (c) Chassis with coil and a servo motor on one side. (d) Assembled robot. (e) Shoe design for improved stability.
• Figure 4: Schematic of the soft robot under applied magnetic fields. .
• Figure 5: Schematic of the PCB: (a) PCB layout diagram showing the placement and routing of components; (b) 3D rendered view of the PCB illustrating the physical appearance of the assembled board.