A weavable DC triboelectric fiber driven by dynamic electric double layers

Abstract

Despite their advantages of direct output and higher power density over AC-TENGs, DC-TENGs face a significant challenge because their performance is highly dependent on environmental humidity. This work successfully addresses device dependence on environmental humidity by developing a novel fiber with a core-sheath structure. The fiber features a platinum wire as the conductive core and a highly hydrophilic sheath (formed from hydrolyzed polyacrylonitrile, h-PAN) that actively captures ambient moisture. The outer layer is coated with a polypyrrole (PPy) semiconductor layer. When the fiber contacts a silver electrode, an interfacial electric field is generated at the contact dielectric. This field polarizes interfacial water molecules and drives directional ion migration, dynamically forming an asymmetric double layer. Collapse occurs when the double-layer structure separates. Through continuous mechanical motion, this process cycles repeatedly, thereby outputting stable direct current. Based on this principle, a single device delivers 300 µA current and 1.8 W m⁻² peak power density at 75% relative humidity, maintaining stability during 200 days of intermittent testing. Through electrode optimization, output can be enhanced to 2 mA current and 73.6 W m⁻² power density. The fiber can be directly woven into breathable fabrics and has successfully provided continuous power to devices like smartwatches. This research establishes a novel design pathway for developing high-power, environmentally adaptable wearable DC power generation systems.