Water-state control unlocks durable and elastic silk fibroin hydrogels.

Protein hydrogels are highly valued for their biocompatibility and biodegradability, yet their practical use has been limited by poor mechanical strength and dehydration. Polymer‒water interactions govern hydrogel mechanics, whereas dehydration causes failure, rendering water retention and hydration-mediated mechanics critical research focuses. Here, we introduce an ion-mediated hydration engineering (IMHE) strategy that reworks the aqueous states within silk fibroin hydrogels via controlled dehydration‒rehydration. This process converts free water into bound water, which enhances chain mobility and stabilizes hierarchical structures. The resulting hydrogel (HSF-MIN) exhibits distinct properties: a 186-fold increase in compressive strength (5.6 MPa), nearly 100% compressible deformation, superelasticity, and long-term stability (maintaining ~80% hydration over 1 year) while maintaining low hysteresis (<5%). These enhancements enable long-term high-performance sensing using low-hysteresis pressure sensors and high-fidelity bioelectric acquisition. We further introduce a water‒polymer interaction model to elucidate the strength‒elasticity synergy. Notably, IMHE also has universality in gelatin hydrogels, thus providing a way for the preparation of high-performance hydrogels.