Figure 7

Thermal tensile actuation for two-end–tethered homochiral yarns. (a) Tensile actuation strain versus temperature before (black) and after (red) wax infiltration for a coiled yarn having an applied stress of 6.8 MPa. Inset: Corresponding actuation data before (black) and after (red) wax infiltration for a non-coiled yarn having an applied stress of 4.8 MPa. (b) Electrothermal tensile actuation strain and work capacity during contraction in vacuum as a function of applied electrical power for a neat, coiled CNT yarn. Insets: Tensile actuation versus estimated temperature for this neat yarn (left) and photograph of the incandescent yarn lifting a 10 g load. Closed symbols and open symbols in (a) and (b) are for increasing and decreasing temperature, respectively. (c) The stress dependence of steady-state tensile actuation and contractile work (black and blue data points, respectively) produced by Joule heating (0.19 V/cm) for a 150-mm-diameter, coiled yarn having different levels of inserted twist [2].