Development of a multiresponsive miniaturized soft robot that can jump in different scenarios is highly desirable. This requires the actuator to simultaneously realize a large bending angle, a fast response,...
This review summarizes the recent progress in twisted-fiber artificial muscles with different methods for preserving the torque and the inserted twist, and explores the relevant applications.
The axial orientation of molecular chains always results in an increase in fiber strength and a decrease in toughness. Here, taking inspiration from the skin structure, artificial spider silk with a buckled sheath–core structure is developed, with mechanical strength and toughness reaching 1.61 GPa and 466 MJ m−3, respectively, exceeding those of Caerostris darwini silk. The buckled structure is achieved by nano‐pulley combing of polyrotaxane hydrogel fibers through cyclic stretch–release training, which exhibits axial alignment of the polymer chains in the fiber core and buckling in the fiber sheath. The artificial spider silk also exhibits excellent supercontraction behavior, achieving a work capacity of 1.89 kJ kg−1, and an actuation stroke of 82%. This work provides a new strategy for designing high‐performance and intelligent fiber materials.
The twistocaloric effect is attributed to the change in entropy of the material driven by torsional stress. It is responsible for the torsional refrigeration of fiber materials that has been widely exploited as one of the solid‐state cooling techniques with high efficiency and low volume change rate. The lack of theories and mathematical models of twistocaloric effect, however, limits broad applications of torsional refrigeration. In this work, a twistocaloric model is established to capture the relationship between twist density and temperature variation of natural rubber fibers and thermoplastic elastomer yarns. An experimental setup consisting torsion actuator and torque sensor coupled with a temperature measurement system is built to validate the model. Using the Maxwell relationship, twistocaloric coefficient is measured by quantifying the thermal effect induced by torsion under shear strain. The experimental characterization of the twistocaloric effect in natural rubber fiber and thermoplastic elastomer yarn are consistent with the theoretical predictions.
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