Water-evaporation-induced direct current electricity generation based on stretchable hydrogel/Al₂O₃

Harvesting sustainable electricity from natural water evaporation has been attracting attention as a promising alternative to supply power for low-power systems. However, low-current output and rigid materials largely hinder its extensive applications. Herein, we present a water-evaporation-induced high-direct-current electricity generator based on stretchable flexible hydrogel/Al₂O₃. This flexible electricity generator forms a porous Al₂O₃ substrate by dissolving the NaCl from the heat-cured gelatin/Al₂O₃/NaCl. It achieves a sustainable and stable direct current of 32 μA, a low internal resistance of 5.18 kΩ, and a maximal output power of 1.76 μW with a maximum output power density of 0.55 mW m⁻² by optimizing the electricity generator's physical dimensions and concentration ratios. The developed water-evaporation-induced electricity generator shows many application prospects, including as a power supply for digital calculators and hygrothermographs and to drive a boat of 5.1 cm. This research provides an in-depth study on a stretchable high-direct-current water-evaporation-induced electricity generator and an efficient approach to power supplies for low-power systems. © 2025 Elsevier Inc.