Piezoresistive Graphene-Based Porous Hydrogels for Dual Applications in Wearable Sensing and Environmental Remediation

This study presents the synthesis of porous hydrogels templated by self-assembled percolating graphene networks. These networks are formed by the spontaneous exfoliation of graphite at oil/water interfaces to form graphene-stabilized emulsions. Compression testing and electrical measurements reveal a reduction in electrical resistance under strain, providing a robust and reliable strain-sensing mechanism with a gauge factor of 13 at a 5% strain. Cyclic compression-relaxation experiments conducted at various strain amplitudes demonstrate reversibility in the mechanical and piezoresistive responses of the hydrogel. Furthermore, variations in crosslinking density significantly affect piezoresistive sensitivity, making these hydrogels particularly suited for real-time motion monitoring applications. When attached to the finger, the change in resistance smoothly varied from ~35% to ~70% as the bend angle increased from 30° to 90°, and importantly, the resistance remained constant when the angle was maintained. In addition to strain sensing, these hydrogels exhibit promising absorptive capabilities, enabling the efficient removal of organic dyes and heavy metal ions through compress-release cycles. The application of an 8V potential approximately tripled the amount of copper ion removal. Overall, the hydrogel's unique combination of elasticity, conductivity, and absorption capabilities highlights its potential in wearable sensor technologies and environmental remediation applications.