Soft Artificial Muscle of Poly(vinyl chloride) Gel with an Imperceptible Liquid Metal Electrode

Electrodes with high electrical conductivity, yet good flexibility and mechanical compliance, are critical for electroactive artificial muscles. Herein, a promising liquid metal (LM) electrode is proposed by transforming eutectic gallium-indium (EGaIn) LM with high surface tension into paste-like LM with solid Ga₂O₃ shells. The developed compliant LM electrode not only shows high conductivity and negligible additional stiffness but also displays excellent electrical stability during cyclic actuation. Based on the LM electrode, the poly(vinyl chloride) gel (PVCG) artificial muscle developed exhibits the maximum actuation strain of 18.7% at a low electric field strength of 9 V μm^-1 and maintains excellent durability without obvious performance attenuation after 10,000 s. A comparison shows that the as-developed PVCG artificial muscle is superior over that based on widely used carbon electrodes. Moreover, an artificial upper limb and crawling worm were manufactured to explore the great potential of PVCG artificial muscle in the robotic field. In addition, the practical application demonstration of the PVCG artificial muscle in the biomimetics field is also successfully fulfilled through the design of reasonable structures. Due to its easy fabrication, excellent electrical conductivity, and high mechanical compliance, the newly developed LM electrode is promising for high-performance PVCG artificial muscles in bionic robots.