Solvent-free and Metal-free Fabrication of Multifunctional Cellulose-Based Fabrics for Wearable Energy Harvesting, Body Motion Detection, and Thermotherapy

Integrating multiple functions into fabrics has provided attractive opportunities for smart wearable technologies. However, it remains challenging to achieve functionalities with fabrics through a facile green pathway suitable for industrialization. Herein, we demonstrate a facile metal-free and solvent-free route to endow commercial fabrics with unified functions utilizing hydroxyethyl cellulose (HEC) and carbon black (CB) via facile dip-coating. Based on the superior compatibility of HEC and CB, incorporating trace amounts of CB (as low as 0.25 wt %) triggers remarkable photo/electro-responsive thermal conversion with rapid responsiveness, appropriate temperatures, and reliable repeatability, verifying wearable heating performances of the modified fabrics. Notably, the resultant fabrics serving as a tribopositive material of triboelectric nanogenerators harnessed electrical signals from minute movements to deliver an open voltage of 321 V, a short current of 3.84 μA, and a transferred charge of 9 nC, and eventually achieved a maximum instantaneous power density up to 2067 mW/m2, showing a significant improvement of 28.2 times higher than that of the original fabric. Furthermore, the fabric-based TENGs effectively deliver instantaneous feedback on human motion and gait analysis, which exhibits good application prospects for detecting and optimizing body postures. The eco-friendly and effective methodology drives the facile and sustainable conversion of commercial fabrics toward wearable healthcare applications.