Architected 3D-printable hydrogels with amplified piezoionic transduction for self-powered wearables

The lack of electronic materials that properly replicate the sensing capabilities of human skin has motivated the search for soft systems that transduce mechanical stimuli through intrinsic physicochemical mechanisms. Piezoionic hydrogels, which under mechanical deformation generate ion flux, offer a promising route toward such functionality. Here we investigate the piezoionic response of a photocurable, self-healing semi-interpenetrating polymer network hydrogel composed of poly(vinyl alcohol), acrylic acid, and poly(ethylene glycol) diacrylate. By systematically varying cation mobility using a series of alkali metal chlorides, we correlate ionic transport with electromechanical output across planar and sandwich electrode configurations under the application of both compressive and tensile mechanical stimuli. Pressure-induced gradients in ionic concentration produce measurable voltage and current outputs when cation and anion mobilities are mismatched, providing a mechanistic analogue to biological mechanoreceptors. We further demonstrate that 3D-printed architecture enhances the piezoionic signal through strain concentration and retain functionality after damage due to the hydrogel's autonomous healing. Finally, we implement these materials as self-powered biometric sensors and mechanical energy harvesters. These results establish a milestone in the design guidelines for ionically driven tactile electronics and highlight that piezoionic materials are cornerstone materials for the next generation of soft robotics, wearable systems, and health-monitoring technologies.