Sensitive, High-Strain, High-Rate Bodily Motion Sensors Based on Graphene–Rubber Composites

TLDR

Monitoring human bodily motion requires wearable sensors that are cheap, lightweight, mechanically compliant, and sensitive at high strains and strain rates, yet no material has met all these criteria. The study aims to create conducting graphene–rubber composites by infusing liquid‑exfoliated graphene into natural rubber. This is achieved by a simple infusion process that yields conductive composites. The resulting composites exhibit 10⁴‑fold resistance changes, gauge factors up to 35, strain limits over 800 %, and can track dynamic strain up to 160 Hz, enabling effective monitoring of joint, muscle, breathing, and pulse motion.

Abstract

Monitoring of human bodily motion requires wearable sensors that can detect position, velocity and acceleration. They should be cheap, lightweight, mechanically compliant and display reasonable sensitivity at high strains and strain rates. No reported material has simultaneously demonstrated all the above requirements. Here we describe a simple method to infuse liquid-exfoliated graphene into natural rubber to create conducting composites. These materials are excellent strain sensors displaying 104-fold increases in resistance and working at strains exceeding 800%. The sensitivity is reasonably high, with gauge factors of up to 35 observed. More importantly, these sensors can effectively track dynamic strain, working well at vibration frequencies of at least 160 Hz. At 60 Hz, we could monitor strains of at least 6% at strain rates exceeding 6000%/s. We have used these composites as bodily motion sensors, effectively monitoring joint and muscle motion as well and breathing and pulse.