Gallic acid integrated conducting PVA hydrogels enhanced by hierarchical energy dissipation system for strain sensor and physiological signal monitoring

Multi-level physical crosslinks build a hierarchical energy dissipation system. • Synergy of PVA domains and dynamic weak bonds balances strength and toughness. • PSGGZ hydrogel reaches 2.13 MPa stress, 539.75% strain, and 574.22 kJ/m 3 toughness. • It exhibits high gauge factor (8.09) and fast responsiveness (38.3 ms) for sensing. Hydrogels represent an important class of intelligent soft materials with wide applications in tissue engineering, flexible sensors, and drug delivery systems. However, their practical deployment has long been severely constrained by the inherent trade-off among mechanical strength, toughness, and ionic conductivity. Herein, a hierarchical energy dissipation system is chosen to construct a hierarchical multi-level physical crosslinking network hydrogel that simultaneously breaks the above performance trade-off. The robust semi-crystalline domains of polyvinyl alcohol (PVA) serve as a rigid backbone to endow the hydrogel with high mechanical strength, while reversible weak interactions including zirconium-oxygen coordination clusters, borate ester bonds, and hydrogen bonds act as sacrificial bonds to dissipate energy efficiently, thus achieving excellent toughness. The stress, strain, elastic modulus and toughness of the optimal hydrogel reach 2.13 MPa, 539.75%, 0.20 MPa, and 5.742 MJ/m 3 , respectively. Simultaneously, the hydrated polymer network enables rapid dissociation and migration of mobile ions, giving the hydrogel prominent strain-responsive conductivity required for sensing applications. The ionic conductivity reaches 2.74 S/m, and the gauge factor is calculated to be 3.79 and 8.09 in the strain ranges of 0–155% and 155%–528%, respectively. Benefiting from the fast dynamic reversibility of the physical network, the response and recovery times are as short as 38.3 ms and 21.9 ms, respectively, endowing the hydrogel with outstanding strain sensing and human motion monitoring capabilities. This work provides a universal design strategy to overcome the mechanical bottleneck of PVA-based hydrogels, paving the way for advanced wearable sensor applications. Download: Download high-res image (246KB) Download: Download full-size image