Triple-Functional, Biodegradable PVA/Okra Polysaccharide Composite Films for Electric Heating, Photothermal Conversion, and Wearable Sensing

Under low-carbon policies, green biodegradable materials such as okra polysaccharide (OP) and poly(vinyl alcohol) (PVA) have gained prominence. In this study, flexible PVA/OP/CA/CB (POAB) composite films are prepared via a simple one-pot method using citric acid (CA) as a cross-linker and carbon black (CB) as a filler. At a safe voltage of 6 V, the surface saturation temperature of the POAB composite films reaches 50 °C, making it a viable option for flexible electric heating devices to help patients alleviate joint pain and stiffness. At a light power density of 1.1 W/cm2, the POAB composite films exhibit a surface saturation temperature as high as 140 °C, demonstrating outstanding photothermal conversion performance. As a wearable strain sensor, POAB composite films feature a wide response range (125%) and excellent cyclic stability (700 s), enabling the monitoring of the range of motion across different joint areas. This assists physicians and rehabilitation therapists in evaluating patients’ recovery progress. Furthermore, after 28 days of biodegradation in soil, it retains its structural integrity with outstanding stability. In summary, POAB composite films enable simultaneous management of the Joule heating effect, photothermal conversion, and wearable strain sensing, contributing to sustainable energy development.