Hydrovoltaic Effect of Microbial Films Enables Highly Efficient and Sustainable Electricity Generation from Ambient Humidity

Hygroelectricity - an interaction between moisture and hydrophilic materials results electricity generation. The whole-cell films are advantageous for sustainable hygroelectric generator (HEG) application because of readily availability, abundance and environmental compatibility, but it is not clear how microbial film affect or interact with hydrovoltaic effect. Herein, four bacteria with different electrochemical activities were used to fabricate whole-cell film-based HEGs. It was found that the optimum HEG produced a high power density of 51 mW/m 2 . The HEG performance mainly depends on five key factors orderly: hydrophilicity > ionization > conductivity > pore structure > water movement. The more hydrophilic groups could induce stronger ion dissociation, diffusion and ionic conductivity by providing more mobile ions, which are driven by water movement. Meanwhile, the porous structure provides channel for water evaporation of interior water molecules, which is a key factor for sustainable hygroelectricity by promoting water cycle in the HEG. Our findings not only reveal an unprecedented hydrovoltaic effect, but also open a new paradigm for developing sustainable electronics with “green” biological materials in Nature