Braided artificial muscles for bio-mimetic actuation under deepwater

Muscles produce high frequency and high stroke linear motions that are essential for animals to achieve superior maneuverability, agility, and environmental adaptability. Artificial muscles are yet to match their biological counterparts, due to the lack of either actuation speed, force, magnitude, or adaptability. Inspired by the hierarchical structure of natural muscles, here we invent new artificial muscles that are powerful, responsive, high stroke, and adaptable. The artificial muscles consist of braided bundles of fibers made of 3D printed liquid crystal elastomer (LCE), and heating threads. The unique hierarchical, braided structure greatly amplifies the actuation performance of the LCE material, which is explained by numerical simulations. In particular, the square knot braid shows reliable cycles of actuation at 1Hz in 3000m depth underwater. Potential application is demonstrated where one bundle of artificial muscles is used to propel a model boat. Looking ahead, our braided artificial muscles could empower novel biomedical devices and soft robots to explore various environments, from inside human body to the mysterious deep sea.