Stomata inspired water control in moisture electricity generators

The performance of moisture electricity generators is highly dependent on environmental humidity, and arid environments induce rapid water loss, limiting their stability and lifetime. Herein, we report a bioinspired smart moisture electricity generator that emulates the stomatal regulation of plants and integrates a thermo-responsive poly(N-isopropylacrylamide) (PNIPAm) coating, a photothermal g-C₃N₄@TiO₂ hydrogel, and asymmetric electrodes on a flexible substrate. The PNIPAm layer undergoes a reversible contact angle transition near its lower critical solution temperature, where hydrogen bonding below this temperature enhances water retention, while its disruption above the lower critical solution temperature causes structural collapse, thereby suppressing moisture evaporation. Meanwhile, the C₃N₄@TiO₂ hydrogel converts sunlight into heat, activating the thermo-responsive behavior of PNIPAm. As a result, the MEG exhibits enhanced output under arid conditions (T > 40 °C and RH < 10%), with the voltage increasing from 0.78 V to 0.81 V and the current density from 46 μA cm −2 to 80 μA cm −2 , while the operational lifetime extends from 32 h to 62 h, nearly twice that of the MEG without the PNIPAm layer.