Carbon nanotube yarn with small outer diameter to maximize the electrochemical performance of artificial muscles

Electrochemically powered carbon nanotube (CNT) artificial muscles have garnered significant attention owing to their chemical stability, low operating voltage, and impressive actuation performance. Notably, twist-based CNT artificial muscles have demonstrated superior actuation performance by maximizing untwisting motion of the CNT yarn. However, the microscopic design of CNTs is yet to be reported, although CNTs comprising CNT yarn muscles are key determinants of performance. Here, we first establish a correlation between the diameter of CNTs and the actuation performance of artificial muscles. The structural reason for the higher deformability is elucidated employing molecular dynamics simulations. The obtained computational simulation results were consistent with the experimentally fabricated yarn. Remarkably, the CNT yarn muscle composed of small-diameter CNTs exhibited a work capacity of 3.57 J/g, significantly higher than previously reported ones. Our findings provide a fundamental design range of CNT diameters that can significantly enhance the performance of electrochemically powered artificial muscles.