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.