Microstructural origin of resistance–strain hysteresis in carbon nanotube thin film conductors

Abstract

A basic need in stretchable electronics for wearable and biomedical technologies is conductors that maintain adequate conductivity under large deformation. This challenge can be met by a network of one-dimensional (1D) conductors, such as carbon nanotubes (CNTs) or silver nanowires, as a thin film on top of a stretchable substrate. The electrical resistance of CNT thin films exhibits a hysteretic dependence on strain under cyclic loading, although the microstructural origin of this strain dependence remains unclear. Through numerical simulations, analytic models, and experiments, we show that the hysteretic resistance evolution is governed by a microstructural parameter ξ (the ratio of the mean projected CNT length over the film length) by showing that ξ is hysteretic with strain and that the resistance is proportional to ξ−2. The findings are generally applicable to any stretchable thin film conductors consisting of 1D conductors with much lower resistance than the contact resistance in the high-density regime.