High-Modulus Homochiral Torsional Oxide Ceramic Artificial Muscles

Fiber-based artificial muscles are soft actuators used to mimic the movement of human muscles. However, using high modulus oxide ceramics to fabricate artificial muscles with high energy and power is a challenge as they are prone to brittle fracture during torsion. Here, a ceramic metallization strategy is reported that solves the problem of low torsion and low ductility of alumina (Al₂O₃) ceramics by chemical plating a thin copper layer on alumina filaments. These filaments with a high modulus of ≈180 GPa can be twisted into chiral coiled artificial muscles, exhibiting a unique electric thermal actuation mechanism. This tough and robust alumina artificial muscle can carry objects equivalent to 0.28 million times its weight and provide high actuation stress of up to 483.5 MPa. In addition, it exhibits 18 times higher contraction power and 240 times higher energy density than human muscles, as well as a high energy conversion efficiency of up to 7.59%, which far exceeds most reported actuated carbon and polymer artificial muscles. This work has achieved large-scale manufacturing of high-modulus oxide ceramic muscles for the first time.