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

• Published in: Advanced functional materials Vol. 32; no. 33
• Main Authors: Yao, Xue, Zhang, Sufeng, Qian, Liwei, Wei, Ning, Nica, Valentin, Coseri, Sergiu, Han, Fei
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.08.2022
• Subjects: Acrylamide; cellulose nanofibrils; conductive hydrogels; Conductors; Healing; Human motion; Hydrogels; Hydrogen bonds; Interpenetrating networks; Ion currents; Ionic liquids; Ions; Materials science; Mechanical properties; Motion sensors; multifunctional sensors; self‐adhesion; self‐healing; Sensors; Strain; Stretchability; Toughness
• DOI: 10.1002/adfm.202204565
• ISSN: 1616-301X

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. A novel semi‐interpenetrating network polyacrylamide/phenylboronic acid‐ionic liquid/cellulose nanofibril hydrogel (PAM/PBA‐IL/CNF) is proposed based on a “tailor‐made” PBA‐IL with multiple roles. Benefiting from the ingenious structural design, the PAM/PBA‐IL/CNF simultaneously displays the excellent comprehensive merits: (i) a fine trade‐off between electrical and mechanical performance, (ii) high strain sensitivity, favorable adhesion, self‐healing property, transparency and water retention.