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.