Ag/BN/EVA Yarn Artificial Muscles with Low Drive Voltage, High Load Capacity, and High Energy Density

In this study, we developed composite fibers composed of silver (Ag)/boron nitride (BN)/ethylene-vinyl acetate copolymer (EVA) utilizing a combination of melt spinning–UV irradiation and chemical Ag-plating techniques. The inclusion of the BN filler was aimed to enhance the thermal conductivity and accelerate the response of EVA, while the application of a nano-Ag coating provided the fiber with high electrical conductivity. The results indicated that the electrical conductivity of the Ag/BN/EVA composite fiber achieved a notable value of 2.47 × 104 S/m. These composite fibers exhibited exceptional two-way shape memory properties, electrothermal conversion characteristics, and electrically driven actuation capabilities. Significantly, we demonstrated that by applying a voltage of merely 2.5 V, it was possible to precisely control the electrically reversible driving strain of the Ag/BN/EVA composite yarn by adjusting the energization time, resulting in an impressive energy density of 99.96 J/kg under a loaded weight (34.50 g), which is approximately 4107 times its own weight (0.0084 g). This led to the development of a composite yarn artificial muscle with a high load-bearing capacity, remarkable energy density, and low driving voltage requirements.