Polymeric ionic liquid modifier as ion-induced crosslinker and functional enhancer: Facile fabrication of multifunctional gelatin hydrogels for flexible electronics.

Gelatin-based ionic conductive hydrogels (ICHs) are promising materials for flexible electronics due to their favorable intrinsic properties, but achieving superior mechanical performance, high conductivity, multifunctionality, and simple fabrication simultaneously is challenging. Inspired by the ion-induced salting-out effect and the tunability of polymeric ionic liquids, poly(1-vinyl-3-carboxymethyl imidazolium fluoride) (PVCIF) was synthesized as an advanced macromolecular modifier and employed in a one-step soaking method to construct gelatin-based ICHs. The fluoride anions in PVCIF induce a salting-out effect, promoting gelatin aggregation and forming robust protein hydrogels. The carboxyl and imidazolium groups in PVCIF engage in multiple non-covalent interactions with gelatin chains, improving energy dissipation and toughness. Additionally, the incorporation of cellulose nanofibers (CNFs) into the hydrogel to create a dual network structure further enhances its mechanical strength and toughness. The optimized hydrogels exhibited excellent mechanical strength (1.28 MPa), stretchability (327.1 %), toughness (2.91 MJ m-3), high electrical conductivity (4.66 mS cm-1), sensitivity (gauge factor = 3.94), antibacterial activity (> 99.2 %), and biocompatibility (cell viability > 95 %). Furthermore, they also displayed temperature-sensitive adhesiveness, frost resistance, water retention, and remoldability. These combined features and the straightforward fabrication process position the gelatin-based ICHs as highly promising for advanced applications in wearable strain sensors for human motion detection.