Biomimetic gradient aerogel fibers for sustainable energy harvesting from human sweat via the hydrovoltaic effect

Sustainable, lightweight, and wearable energy harvesting technologies present significant opportunities to address the limitations of traditional power devices such as rigidity and bulkiness. Inspired by the efficient water transport mechanisms in plant roots, we developed a microfluidic spinning system to produce gradient nanoporous cellulose/CNTs aerogel fibers (GAFs) continuously. These GAFs enable rapid water transport and improved evaporation, resulting in a stable flow potential output of 510 mV per 1 cm fiber, higher than the 448 mV achieved by uniform porous fibers. Additionally, GAFs demonstrate high output performance (>400 mV) across varying fiber lengths, electrolyte compositions, temperatures, humidity levels, and wind speeds. When incorporated into a fabric array, GAFs provided stable energy harvesting, delivering an output voltage of 4.5 V and a current of 60 μA under conditions simulating human sweat. This output is sufficient to power a wristwatch. The study introduces a bioinspired nanostructure design for efficient energy harvesting, advancing the development of flexible wearable electronics.