Circadian humidity fluctuation induced capillary flow for sustainable mobile energy

• Published in: Nature communications Vol. 13; no. 1; p. 1291
• Main Authors: Tang, Jiayue, Zhao, Yuanyuan, Wang, Mi, Wang, Dianyu, Yang, Xuan, Hao, Ruiran, Wang, Mingzhan, Wang, Yanlei, He, Hongyan, Xin, John H., Zheng, Shuang
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11.03.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 147/135; 639/301/357; 639/766/189; Absorption; Arrays; Capillary flow; Circadian rhythms; Clean energy; Desorption; Droplets; Drops (liquids); Electric contacts; Electricity; Energy sources; Flow velocity; Generators; Humanities and Social Sciences; Humans; Humidity; Ionic liquids; Ions; Liquid-vapor interfaces; Moisture; Moisture absorption; multidisciplinary; Nanotechnology; Nanowires; Renewable Energy; Science; Science (multidisciplinary); Spherical caps; Surface Tension; Water
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-28998-y

Circadian humidity fluctuation is an important factor that affects human life all over the world. Here we show that spherical cap-shaped ionic liquid drops sitting on nanowire array are able to continuously output electricity when exposed to outdoor air, which we attribute to the daily humidity fluctuation induced directional capillary flow. Specifically, ionic liquid drops could absorb/desorb water around the liquid/vapor interface and swell/shrink depending on air humidity fluctuation. While pinning of the drop by nanowire array suppresses advancing/receding of triple-phase contact line. To maintain the surface tension-regulated spherical cap profile, inward/outward flow arises for removing excess fluid from the edge or filling the perimeter with fluid from center. This moisture absorption/desorption-caused capillary flow is confirmed by in-situ microscope imaging. We conduct further research to reveal how environmental humidity affects flow rate and power generation performance. To further illustrate feasibility of our strategy, we combine the generators to light up a red diode and LCD screen. All these results present the great potential of tiny humidity fluctuation as an easily accessible anytime-and-anywhere small-scale green energy resource. Droplet generators convert mechanical movements of droplets into small-scale electricity. Here, Tang et al . report a humidity-driven power generator by utilizing daily humidity fluctuation in atmosphere enabling continuous generation of electricity upon moisture absorption and desorption cycles.