Abstract
Abstract High performance torsional and tensile artificial muscles are described, which utilize thermally- or electrochemically-induced volume changes of twist-spun, guest-filled, carbon nanotube (CNT) yarns. These yarns were prepared by incorporating twist in carbon nanotube sheets drawn from spinnable CNT forests. Inserting high twist into the CNT yarn results in yarn coiling, which can dramatically amplify tensile stroke and work capabilities compared with that for the non-coiled twisted yarn. When electrochemically driven in a liquid electrolyte, these artificial muscles can generate a torsional rotation per muscle length that is over 1000 times higher than for previously reported torsional muscles. All-solid-state torsional electrochemical yarn muscles have provided a large torsional muscle stroke (53° per mm of yarn length) and a tensile stroke of up to 1.3% when lifting loads that are ~25 times heavier than can be lifted by the same diameter human skeletal muscle. Over a million torsional and tensile actuation cycles have been demonstrated for thermally powered CNT hybrid yarns muscles filled with paraffin wax, wherein a muscle spins a rotor at an average 11,500 revolutions/minute or delivers 3% tensile contraction at 1200 cycles/minute. At lower actuation rates, these thermally powered muscles provide tensile strokes of over 10%.
Highlights
Carbon nanotube (CNT) sheets drawn from spinnable CNT forests has been investigated for such applications as actuators [1,2,3], supercapacitors [4,5], solar cells [6], biofuel cells [7], and acoustic speaker [8]
Zhang et al developed methods to produce these sheets from spinnable CNT forest [9] and Lima et al exploited these sheets for their biscrolling process, in which guest-coated CNT sheets are spun into yarn in which the guest is trapped in helical yarn corridors [10]
We describe methods for producing high performance CNT-based torsional and tensile artificial muscles by processes that involve inserting twist into forest-drawn CNT sheets
Summary
Carbon nanotube (CNT) sheets drawn from spinnable CNT forests has been investigated for such applications as actuators [1,2,3], supercapacitors [4,5], solar cells [6], biofuel cells [7], and acoustic speaker [8]. Zhang et al developed methods to produce these sheets from spinnable CNT forest [9] and Lima et al exploited these sheets for their biscrolling process, in which guest-coated CNT sheets are spun into yarn in which the guest is trapped in helical yarn corridors [10]. We describe methods for producing high performance CNT-based torsional and tensile artificial muscles by processes that involve inserting twist into forest-drawn CNT sheets. All of these muscles use yarn volume expansion (produced either electrochemically or by thermal expansion of a yarn guest) to reversibly generate yarn contraction and yarn untwist [1,2]. Yarn coiling, produced by inserting high twist into the CNT yarn, Lee et al Nano Convergence (2015): dramatically amplifies tensile stroke and work capabilities compared with those for non-coiled yarn [2]
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