Highly Stretchable Sheath-Core Yarns for Multifunctional Wearable Electronics

Flexible electronic devices with strain sensing and energy storage functions integrated simultaneously are urgently desirable to detect human motions for potential wearable applications. This paper reports the fabrication of a cotton/carbon nanotube sheath-core yarn deposited with polypyrrole (PPy) for highly multifunctional stretchable wearable electronics. The microscopic structure and morphology of the prepared sheath-core yarn were characterized by scanning electron microscopy and Fourier transform infrared spectrometry. A mechanical experiment demonstrated its excellent stretchable capacity because of its unique spring-like structure. We demonstrate that the sheath-core yarn can be used as wearable strain sensors, exhibiting an ultrahigh strain sensing range (0-350%) and excellent stability. The sheath-core yarn can be used in highly sensitive real time monitoring toward both subtle and large human motions under different conditions. Furthermore, the electrochemical performance of the sheath-core yarn was characterized by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The measured areal capacitance was 761.2 mF/cm² at the scanning rate of 1 mV/s. The method of spinning technology may lead to new exploitation of CNTs and PPy in future wearable electronic device applications.