Self-healing waterborne polyurethane/bacterial cellulose composite flexible electronic skin based on Diels-Alder dynamic covalent bonds: Preparation, mechanical properties, and sensing performance

High mechanical strength (41.5 MPa) and self-healing efficiency (119%) achieved via DA dynamic covalent bonds and BC reinforcement. • BC-dispersed MWCNTs enable high sensitivity (GF = 10.15) and stable sensing over 0–130% strain. • The flexible electronic skin enables real-time monitoring of joint motions and ECG/EMG signals. Conventional waterborne polyurethane (WPU)-based flexible sensors often exhibit insufficient strength, limited self-healing capacity, and unstable cyclic performance. Herein, a self-healing WPU/bacterial cellulose (BC) composite matrix was fabricated by combining BC nanofiber reinforcement with thermally reversible Diels-Alder (DA) dynamic covalent bonds. Multi-walled carbon nanotubes (MWCNTs) were incorporated as the conductive phase. BC nanofibers interweave with WPU chains to provide topological confinement, while interfacial hydrogen bonding and physical entanglement anchor the polymer chains. At a BC loading of only 5‰, the composite achieved a tensile strength of 41.5 MPa and an elongation at break of 674%. The reversible DA bonds mitigate the trade-off between mechanical strength and self-healing, yielding a self-healing efficiency of 119% after thermal treatment, together with good thermal stability and recyclability. BC also suppresses MWCNT agglomeration and promotes the formation of stable conductive networks. The resulting films exhibited a gauge factor (GF) of 10.15, a stable sensing response over a strain range of 0–130%, and the ability to detect human motion, electromyographic, and electrocardiographic signals. These multifunctional composite films combine mechanical robustness, self-healing performance, and reliable sensing behaviour, indicating their potential for wearable electronics and physiological monitoring. Download: Download high-res image (146KB) Download: Download full-size image