A Recyclable and Biodegradable High-Performance Piezoelectric Nanogenerator for Self-Powered Biosensing and Assistive Human-Machine Interaction.

The escalating global challenge of electronic waste demands energy-harvesting materials that deliver high performance without compromising environmental sustainability. We present a molecularly engineered, fully biodegradable piezoelectric nanogenerator (PENG) based on a composite of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (TOCNF) and 2,2,3,3,4,4-hexafluoropentane-1,5-diol (HFPD). Multiscale hydrogen bonding orchestrates a hierarchically ordered structure, yielding an exceptional piezoelectric coefficient of 14.0 pC·N-1 and excellent fatigue durability (100 000 bending cycles). This PENG exhibits high sensitivity for real-time monitoring of human physiological signals, from limb movements and joint kinematics to speech and respiration. Integrated with a deep learning framework, the system achieves 98.7% accuracy in recognizing Morse code signals, offering a novel assistive communication tool. In vivo experiments demonstrate its capability to capture limb motion and respiratory signals, confirming its potential for implantable biomonitoring. Crucially, the device is fully recyclable in water without performance loss and biodegrades in soil within 25 days. This work provides a scalable design strategy for functional materials that unify high performance with full lifecycle sustainability, charting a transformative path toward environmentally benign electronics.