Thermally driven carbon nanotube@polycaprolactone coaxial artificial muscle fibers working in subzero environments

Artificial muscle fibers driven electrothermally with excellent properties of response, stroke, and work capacity are expected to serve in some intelligent structures and systems. However, muscle fibers that operate in subzero environments are highly needed in industrial production and aerospace applications but remain challenging. Herein, we reported a coaxial artificial muscle fiber by electrospinning a sheath of polycaprolactone (PCL) nanofibers on the surface of a carbon nanotube (CNT) fiber core, achieving the actuation in response to thermal at subzero temperatures. The CNT@PCL coaxial muscle fiber under 0.3 MPa achieved a maximum contractile stroke of ~18% as the temperature changed from −130°C to 45°C. The actuation mechanism at subzero temperatures of this muscle fiber was analyzed in combination with the temperature-deformation schematic curve of different polymers. Furthermore, a temperature sensor based on this muscle fiber was developed, due to the excellent linear relationship between the contraction and temperature. A 3D-printed prosthetic arm was designed to further exhibit the application demonstrations of this muscle fiber in subzero environments. This work provides new insights into artificial muscle fibers for serving in extreme environments with ultralow temperatures.