Hydraulic hydrogel actuators and robots optically and sonically camouflaged in water

TLDR

Sea animals such as leptocephali use transparent hydrogels for agile motion and camouflage, yet current hydrogel actuators are slow, low‑force, and lack camouflage capabilities. The study develops hydraulic hydrogel actuators that mimic leptocephali, achieving high‑speed, high‑force operation with optical and sonic camouflage in water. These actuators and robots demonstrate durable, high‑performance motion, swimming, kicking rubber balls, and even catching live fish while maintaining robustness over multiple cycles.

Abstract

Abstract Sea animals such as leptocephali develop tissues and organs composed of active transparent hydrogels to achieve agile motions and natural camouflage in water. Hydrogel-based actuators that can imitate the capabilities of leptocephali will enable new applications in diverse fields. However, existing hydrogel actuators, mostly osmotic-driven, are intrinsically low-speed and/or low-force; and their camouflage capabilities have not been explored. Here we show that hydraulic actuations of hydrogels with designed structures and properties can give soft actuators and robots that are high-speed, high-force, and optically and sonically camouflaged in water. The hydrogel actuators and robots can maintain their robustness and functionality over multiple cycles of actuations, owing to the anti-fatigue property of the hydrogel under moderate stresses. We further demonstrate that the agile and transparent hydrogel actuators and robots perform extraordinary functions including swimming, kicking rubber-balls and even catching a live fish in water.