Stress-sensitive thermally conductive elastic nanocomposite based on interconnected graphite-welded carbon nanotube sponges

Abstract

Stress-sensitive thermally conductive elastic materials are necessary for designing flexible, thermal-sensitive devices such as sensors or skins. However, combining high thermal conductivity (k) and good cyclic resilience (elastic deformation) is challenging according to the Newton−Laplace equation. This study presents a graphite-welded carbon nanotube (w-CNT) sponges as a three-dimensional skeleton for polydimethylsiloxane (PDMS) composites. Welds of discontinuous CNT with graphite layers promote phonon and stress transfer at the junctions. The interconnected network and uniform closely packed polymers not only enable stress-sensitive heat conduction but also retain excellent cyclic elastic deformability and good resilience. The composite combines a stress-sensitive isotropic k and excellent elastic deformation. The w-CNT/PDMS composite at the content of 4.57 wt% w-CNT exhibits a high k up to 13.1 W m−1 K−1 at 29.2% compressive strain. The composite also retains high k with the loss of 2% after 100000 compression cycles. The stress-sensitive w-CNT/PDMS composite enable it to be used in a flexible thermal-sensitive strain sensor. The bending and stretching of the finger are tracked by thermochromic changes controlled by stress-enhanced heat conduction. The stress-sensitive thermally conductive w-CNT/PDMS composites can be developed for a multitude of flexible sensors by optimizing their microstructures.