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While previous guest-filled carbon nanotube yarn muscles provide remarkable performance, whose actuation is driven by the volume change of a guest. They also have problems. For instance (a) carbon nanotube yarns are expensive and (b) input energy is provided to the entire muscle, but the central region of the muscle contributes little to muscle contraction. Here, we eliminated this problem by driving the muscle using a sheath, which can be on an inexpensive coiled yarn or fiber core. This configuration change dramatically increases muscle power and enables cheap commercialized yarns to replace expensive carbon nanotube yarns. For different application purposes, we coated different types of polymer or other materials to optimized the actuation performance under different trigger conditions. For instance, the electrochemical SRAM which using the CNT as the sheath and Nylon 6 yarn as the core can generate 1.98 W/g of average contractile power - 40 times that for human muscle and 9.0 times that of the highest power alternative electrochemical muscle. The electrothermal PEO-SO3@CNT SRAMs (PEO-SO3 as the sheath and CNT as the core) operated in air and in room-temperature water to produce 2.6 W/g (at 9 Hz) and 9.0 W/g (at 12 Hz) of full-cycle contractile power, respectively, compared with the 0.05 W/g typical of human muscle. Additionally, coating vapors or moisture response material on the twisted core material, we can obtain a muscle which operates torsional and tensile actuation under different vapor concentration or humidity. Because sheath-run muscles can be made so cheaply without using carbon nanotubes, and are easily upscaled, we fabricated a comfort adjusting textiles that respond to temperature, humidity and the presence or absence of perspiration by opening and closing pores(1).
Reference (1) Mu, Jiuke, et al. "Sheath-run artificial muscles." Science 365.6449 (2019): 150-155.
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