# Bioinspired Twisted Artificial Muscles with Enhanced Performance for Underwater Applications

## TL;DR

A new type of artificial muscle inspired by climbing plants and seal blubber improves performance in underwater robots.

## Contribution

A bioinspired TAM configuration with braided fibers and thermal insulation for enhanced underwater actuation.

## Key findings

- The TAM achieves a 40% contraction ratio under 300 g load and 180° s−1 angular velocity in water.
- Thermal insulation reduces heat dissipation by creating a 30.5°C temperature difference underwater.
- A bionic ray demonstrator achieves 105 mm straight motion and 30° turning in a single actuation cycle.

## Abstract

Twisted artificial muscles (TAMs) demonstrate great promise in robotic applications involving locomotion and manipulation. However, their functionality in underwater environments remains challenging due to limitations in deformation, output force, and heat dissipation especially for thermally driven TAMs. To address these challenges, a novel TAM configuration inspired by the twining structures of climbing plants that consists of braided and pre‐twisted fiber bundles is proposed. This configuration achieves large deformation and high output force, reaching a contraction ratio of 40.0% under a load of 300 g. Meanwhile, a soft insulation layer inspired by the blubber layer of seals is applied to reduce heat dissipation in underwater environments, resulting in a 30.5 °C temperature difference. In addition, a rapid actuation unit is developed, which utilizes elastic energy storage and release to achieve an angular velocity of 180° s−1 in water. Finally, a bionic ray driven by the proposed TAMs is developed as a demonstrator, achieving a displacement of 105 mm for straight motion and a turning angle of 30° within a single actuation cycle. These results highlight the strong potential of the proposed TAMs for underwater application.

A climbing plant‐inspired twisted artificial muscle (TAM) with a braided configuration and seal‐inspired thermal insulation enables high‐performance underwater actuation. Enhanced deformation, reduced heat dissipation, and rapid motion are validated through a bionic ray that exhibits straight and turning motions. This work highlights the potential of TAMs for underwater applications.