Stepwise salting-out and freeze-thaw strategy enables robust conductive polyvinyl alcohol hydrogels via interfacial synergy for multifunctional wearables.

Abstract

To address the intrinsic trade-off between mechanical robustness and ionic conductivity in polyvinyl alcohol (PVA) hydrogels arising from structural heterogeneity, this work presents a stepwise salting-out and freeze-thaw cycling strategy to fabricate high-performance composite hydrogels with synergistic interfacial interactions. By integrating sodium alginate-dispersed liquid metal with lignosulfonate mediation, we establish a multi-scale crosslinking network governed by hydrogen bonding, metal-coordination, and electrostatic effects. Crucially, the stepwise process mitigates the excessive densification typical of conventional methods, facilitating the homogeneous infiltration of additives and refining PVA microcrystalline domains. The optimized hydrogel achieves a tensile strength of 1.22 ± 0.04 MPa and an ionic conductivity of 1.7 ± 0.05 S·m-1-representing enhancements of 1406% and 765% over pristine PVA, respectively-while exhibiting exceptional fatigue resistance with negligible hysteresis decay over 2000 loading-unloading cycles. Additionally, the hydrogel demonstrates versatile functionality as strain sensors, triboelectric nanogenerators, and bioelectrodes; notably, integration with a one-dimensional convolutional neural network deep learning model enables a self-powered system to achieve 91.76% accuracy in gait pattern recognition. This study provides fundamental understanding of interfacial synergy in physically crosslinked hydrogels, paving the way for durable soft colloidal materials.