Knittable Composite Fiber Allows Constant and Tremendous Self‐Powering Based on the Transpiration‐Driven Electrokinetic Effect

Abstract The electrokinetic effect allows harvesting renewable energy directly from moisture, sweat, and rainwater, which is one of the promising techniques for self‐powered electronics. However, current fibrous hygroelectric nanogenerators still suffer from either an intermittent energy harvesting mode or a limited electricity supply. Herein, learning from the transpiration process in plants, a conductive and hydrophilic cellulose/carbon nanotubes fiber is reported, in which continuous and efficient water flow can be driven by the macromolecular chain channel and spontaneous evaporation. In combination with the electrokinetic mechanism, just a single self‐powered fiber is found to produce a constant and tremendous open‐circuit voltage of 160.4 mV and a considerable power density up to 0.4 mW cm −3 . This record‐high output performance with the feature of continuity and durability is about one order of magnitude higher than that of most conventional fibrous hygroelectric nanogenerators. Eventually, 108 fibers in series or parallel are woven into flexible fabrics, yielding the maximum power supply of 1.2 V with only 10 min charging time, capable of powering an electronic calculator. This work fabricates a knittable and designable self‐powering fiber with excellent aesthetics and comfort for practical application, offering a novel concept and an effective approach toward clean energy usage.