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℃ to 45℃.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.

High‑Temperature‑Tolerant Artificial Muscles Using Poly(p‑phenylene benzobisoxazole)Composite Yarns

Today the developed yarn muscles or actuators still cannot satisfy the requirements of working in high-temperature environ-ments.Thermal resistivity is highly needed in aerospace and industrial protection applications.Herein,an artificial muscle with high-temperature tolerance is prepared using carbon nanotube(CNT)wrapped poly(p-phenylene benzobisoxazole)(PBO)composite yarns.A thermal twisting method was utilized to reorientate the stiff PBO molecular chains into a uniform and twist-stable coiled structure.The CNT/PBO composite yarn muscle generates reversible contractile strokes up to 18.9%under 5.4 MPa tension and outputs 1.3 kJ kg^(-1) energy density.In contrast to previous actuators,which are normally oper-ated at room temperatures,the CNT/PBO composite yarn muscles can work at ambient temperatures up to 300℃ with high contractile stroke and long-term stability.A bionic inchworm robot,a deployable structure,and smart textiles driven by the high-temperature-tolerant yarn muscles were demonstrated,showing the promise as a soft actuator towards high-temperature environment applications.