Biodegradable Ecoflex encapsulated bacterial cellulose/polypyrrole strain sensor detects motion with high sensitivity, flexibility and scalability

Microbial production of biopolymers are non-standard materials in wearable resistive-strain sensors, despite established and desirable scale-up, rheological, ecological and economical properties. In this study, we report a biodegradable bacterial cellulose (BC) crack-based strain sensor prepared by in-situ fermentation with polypyrrole (PPy) and encapsulation with Ecoflex (EF) for human-interactive sensing. In-situ microbial fermentation method not only optimizes the distribution state of PPy but also constructs the three-dimensional conductive network, which contributing to the formation of crack-based sensing mechanism. The as-prepared BC/Ppy@EF strain sensor exhibits high sensitivity (gauge factor of 3.21-4.86), large strain ranges (up to 90% strain), ultralow strain detection limit (0.05%) and remarkable long-term stability without any distinct decline in sensitivity after a constant applied stretching of 90% for 1000 cycles. The strain sensor accurately detected a full range of body motions, including subtle vital signs like pulse, respiration and vocalizations, and was successfully integrated into textiles for human-computer interactions. Consequently, this study provides empirical value for the biofabrication and all-green construction design of wearable devices, as well as the development of human-computer interaction.