Electron transport engineering of carbon hybrid network towards physiological signal monitoring and efficient heat management

Abstract

E-skin that can mimic the complex functions of human skin has attracted considerable interest in health monitoring and medical diagnosis. However, the accurate and reliable detection of multiple external stimuli using a sole sensing component remains challenging. Herein, we describe a flexible strain-temperature sensor fabricated by employing conductive 1D multi-walled carbon nanotubes (MWCNTs), 2D reduced graphene oxide (RGO) and a flexible polydimethylsiloxane (PDMS) substrate to construct a sandwich structure. Consequently, the flexible MWCNTs@RGO hybrid film with optimized conductivity exhibits a high gauge factor (GF = 1888) at a strain up to 40 %, prominent long-term durability (8000 cycles at 25 % strain), low strain detection (0.05 %) and rapid response (57 ms). The significantly enhanced performance is attributed to the synergy of tubular MWCNTs and layered RGO, as revealed by finite element analysis. Additionally, the hybrid film sensor exhibits temperature-sensing ability with a typical negative temperature coefficient of resistance and delivers an improved sensitivity upon thermal stimulus via prestrain-induced microcracks and a thermal expansion strategy. Owing to its excellent sensing properties, it can not only detect human motions in various situations but also be adopted as a temperature warning/cooling system, supporting its feasibility for use by patients lacking temperature perception and bringing convenience to daily life.