Super Stretchable, Self-Healing, Adhesive Ionic Conductive Hydrogels Based on Tailor-Made Ionic Liquid for High-Performance Strain Sensors

Abstract

Ionic conductive hydrogels (ICHs) integrate the conductive performance and soft nature of tissue-like materials to imitate the features of human skin with mechanical and sensory traits; thus, they are considered promising substitutes for conventional rigid metallic conductors when fabricating human-motion sensors. However, the simultaneous incorporation of excellent stretchability, toughness, ionic conductivity, self-healing, and adhesion via a simple method remains a grand challenge. Herein, a novel ICH platform is proposed by designing a phenylboronic acid-ionic liquid (PBA-IL) with multiple roles that simultaneously realize the highly mechanical, electrical, and versatile properties. This elaborately designed semi-interpenetrating network ICH is fabricated via a facile one-step approach by introducing cellulose nanofibrils (CNFs) into the PBA-IL/acrylamide cross-linked network. Ingeniously, the dynamic boronic ester bonds and physical interactions (hydrogen bonds and electrostatic interactions) of the cross-linked network endow these hydrogels with remarkable stretchability (1810 ± 38%), toughness (2.65 ± 0.03 MJ m⁻³), self-healing property (92 ± 2% efficiency), adhesiveness, and transparency. Moreover, the construction of this material shows that CNFs can synergistically enhance mechanical performance and conductivity. The wide working strain range (≈1000%) and high sensitivity (GF = 8.36) make this ICH a promising candidate for constructing the next generation of gel-based strain sensor platforms.