Abstract
Highly deformable and electrically conductive fibres with multiple functionalities may be useful for diverse applications. Here we report on a supercoil structure (i.e. coiling of a coil) of fibres fabricated by inserting a giant twist into spandex-core fibres wrapped in a carbon nanotube sheath. The resulting supercoiled fibres show a highly ordered and compact structure along the fibre direction, which can sustain up to 1,500% elastic deformation. The supercoiled fibre exhibits an increase in resistance of 4.2% for stretching of 1,000% when overcoated by a passivation layer. Moreover, by incorporating pseudocapacitive-active materials, we demonstrate the existence of superelastic supercapacitors with high linear and areal capacitance values of 21.7 mF cm-1 and 92.1 mF cm-2, respectively, that can be reversibly stretched by 1,000% without significant capacitance loss. The supercoiled fibre can also function as an electrothermal artificial muscle, contracting 4.2% (percentage of loaded fibre length) when 0.45 V mm-1 is applied.
Highlights
Deformable and electrically conductive fibres with multiple functionalities may be useful for diverse applications
The fibres injected with a liquid metal were reported to have excellent stretchy-invariant electrical conductivity because of high viscosity of the liquid metal, this method is based on expensive elements and needs to be contained in hollow structured containers to prevent leakage, which limits wider application
Due to the high degree of structural compaction, by storing large linear strain in the fibre tensile direction, the supercoiled fibres exhibit superelasticity (~ 1500%) without significant electrical fracture. This high degree of structural organisation can store the ultra-high linear strain, and allow the supercoil structure to be used for extendable conductive transmission lines, pseudocapacitive supercapacitors, and artificial muscles
Summary
Deformable and electrically conductive fibres with multiple functionalities may be useful for diverse applications. From a structural aspect, microscopically buckled structures[1,9,10,11], macroscopically coiled structures[2,3,12,13,14,15,16], or a combination of both[17] were employed for carbon nanotube (CNT) yarns or twist-spun CNT sheet-wrapped fibres to provide structural stretchability These buckled or coiled fibres exhibited relatively high electrical and elastic properties and were demonstrated to be effective electrodes for elastic sensors[1,10,11] and energy storage[2,3,9,10,15]. This high degree of structural organisation can store the ultra-high linear strain, and allow the supercoil structure to be used for extendable conductive transmission lines, pseudocapacitive supercapacitors, and artificial muscles
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