Nanofibrous Matrix\nMediated Ultrasensitive Flexible\nStrain Sensor for Subtle Human Motion Monitoring

Abstract

Flexible strain sensors have attracted extensive research\ninterest\nin health monitoring and early diagnosis owing to their superiority\nin continuous measurement of physiological signals. However, the design\nof flexible sensors with high sensitivity for subtle strain measurement\ncoupled with biocompatibility, breathability, and eco-friendly properties\nis still challenging. In this study, a facile and universal approach\nwas developed for the preparation of highly sensitive, biocompatible,\nand eco-friendly flexible strain sensors in reduced graphene oxide\n(rGO)/silk composites. The microcrack structures generated in rGO\nfunctional layers were achieved by vacuum filtration of GO onto silk\nnanofibrous matrices followed by a reduction process. The optimized\nflexible sensor exhibited high sensitivity with a gauge factor (GF)\nof 436 and 204 at a stretching strain of 8–8.7% and a bending\nstrain of 0.12%, respectively. The sensor also revealed a superfast\nresponse of 8.8 ms, excellent durability for over 2000 cycles of bending,\nand waterproof ability up to 80 °C after 9 cycles. The degradability\nof the silk substrates enables the recycling of conductive materials,\nleading to eco-friendly sensor materials. The optimized rGO/silk sensor\nwas able to sensitively and stably detect physiological signals with\nsubtle strain changes (voices, pulse, and airflow), demonstrating\ngreat potential for use in flexible strain sensing of human health\nmonitoring and medical diagnostics.