Ultrasensitive and robust self-healing composite films with reinforcement of multi-branched cellulose nanocrystals

Abstract

Herein, self-healing multi-branched cellulose nanocrystals/polyvinyl alcohol (MCNC/PVA) composite films with excellent sensitivity to human motions was synthesized by employing MCNC as reinforcing agent, where the potassium chloride (KCl) was added to enhance the conductivity and strain sensitivity of the composite film. There was a synergistic effect between MCNC and PVA, which could promote the slip and recombination of hydrogen bonds, so that the films had robust strength (2.2 times to pure PVA) and high self-healing efficiency (69.54% after 20 min). Especially, the flexible composite film could clearly monitor both large and subtle human motions (finger bending, swallowing, breathing, and insect crawling), and showed larger subtle strain sensitivity (strains <24.5%) with a gauge factor (GF) of 2.4, which was relatively larger than the GF of ionic hydrogel and film-based skin sensors, which could solve the current problems of poor mechanical flexibility and low sensitivity of electronic skin, and had great potential application in the fields of self-healing soft electronic skin sensors for human motion detection and healthcare.