Mechanically Enhanced, Environmentally Stable, and Bioinspired Charge-Gradient Hydrogel Membranes for Efficient Ion Gradient Power Generation and Linear Self-Powered Sensing

The soft hydrogel power source is an interesting example of generating electricity from clean energy. However, ion-selective hydrogel membranes in the systems are often limited by low ion selectivity, high membrane resistance, insufficient mass transfer, and ion concentration polarization, resulting in a generally low power output. Inspired by the unique structure of the electric ray's electric organ, a vertically stacked hydrogel artificial electric organ is proposed, aiming to increase the output current to a greater extent. By constructing the charge gradient in ultrathin ion-selective hydrogel membranes, ion transport is accelerated while mitigating the ion concentration polarization. A single hydrogel artificial electric organ achieves high outputs of ≈290 mV and ≈1.46 mA cm⁻² with rechargeability, surpassing similar devices. Density functional theory further reveals that the energy barrier of ion transport in charge-gradient membranes is lower than that in nongradient membranes. More impressively, the device can still be applied as a linear self-powered pressure sensor for monitoring human activities after the ion gradient is completely dissipated. This study elucidates the key role of the structure and design of ion-selective membranes in the artificial gel power generation system, providing new insights into the further development and multifunctional application of flexible gel power source.