Solvent-Exchange-Induced Dual-Interaction Eutectogels with Integrated Sensing and Gait-Pattern Recognition Capabilities.

Abstract

Deep eutectic solvent (DES)-based gels combine low volatility with ionic conductivity for soft sensing, but balancing mechanical compliance, interfacial adhesion, and ion transport remains challenging. Here, a post-formation solvent-exchange strategy is employed to reconstruct a physically crosslinked poly(vinyl alcohol) (PVA) network using a Fe3+-containing DES. Spectroscopic, structural, and computational analyses reveal a reconstructed interaction environment in which hydrogen bonding coexists with Fe3+-mediated interactions, accompanied by extensive disruption of ordered PVA chain packing. The resulting UFP eutectogel exhibits a tensile strength of 0.43 MPa, a fracture strain of 423%, a toughness of 0.62 MJ·m-3, and an ionic conductivity of 0.42 S·m-1, together with reversible multisubstrate adhesion and improved resistance to solvent loss. UFP supports independently configured strain and pressure sensing and can be integrated into a 3 × 3 array for spatial pressure-pattern mapping. An encapsulated plantar sensor further generates distinguishable resistance waveforms for four simulated gait patterns, enabling proof-of-concept pattern classification using a neural-network model. These results demonstrate post-formation solvent exchange as an effective approach for regulating the balance among mechanical compliance, ionic transport, adhesion, and sensing functionality in PVA-based eutectogels.