Highly twisted supercoils for superelastic multi-functional fibres.

Son, Wonkyeong; Chun, Sungwoo; Lee, Jae Myeong; Lee, Yourack; Park, Jeongmin; Suh, Dongseok; Lee, Duck Weon; Jung, Hachul et al. · Nat Commun · 2019

basic_science · Level V

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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<sup>-1</sup> and 92.1 mF cm<sup>-2</sup>, 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<sup>-1</sup> is applied.