Tough and Highly Efficient Underwater Self‐Repairing Hydrogels for Soft Electronics

Abstract

The vulnerability of hydrogel electronic materials to mechanical damage due to their soft nature has necessitated the development of self‐repairing hydrogel electronics. However, the development of such material with underwater self‐repairing capability as well as excellent mechanical properties for application in aquatic environments is highly challenging and has not yet been fully realized. This study designs a tough and highly efficient underwater self‐repairing supramolecular hydrogel by synergistically combining weak hydrogen bonds (H‐bonds) and strong dipole–dipole interactions. The resultant hydrogel has high stretchability (up to 700%) and toughness (4.45 MJ m−3), and an almost 100% fast strain self‐recovery (10 min). The underwater healing process is rapid and autonomous (98% self‐repair efficiency after 1 h of healing). Supramolecular hydrogels can be developed as soft electronic sensors for physiological signal detection (gestures, breathing, microexpression, and vocalization) and real‐time underwater communication (Morse code). Importantly, the hydrogel sensor can function underwater after mechanical damage because of its highly efficient underwater self‐repairing capability.

Recent advances in electronic skins: material progress and applications

“…By combining weak hydrogen bonds and strong dipole-dipole interactions, Fu et al designed a tough and efficient underwater self-healing supramolecular hydrogel ( Fu et al, 2022 ). The hydrogel has high stretchability (up to 700%), toughness, and an almost 100% fast strain self-recovery.…”

Anti-Swelling Zwitterionic Hydrogels as Multi-Modal Underwater Sensors and All-in-One Supercapacitors

“…Soft electronics have attracted tremendous interest for their large application potential in the fields of flexible sensors, − biomedical devices, − electronic skins, − and so on. Among them, gel-based electronics are specifically preferred for their tissue-like structure, good biocompatibility, and considerable toughness. − Although enormous efforts have been paid for developing stretchable and highly sensitive electronics, constructing tough gel-based sensors capable of detecting signals underwater remains a big challenge yet is very crucial for ocean exploration. − Most of the existing flexible sensors are not suitable for an aqueous environment, as a result of the instability of the polymer backbone and uncontrollable spreading of conductive ions/nanoparticles in water, which finally result in the decline of mechanical and electrical performance. − …”

Double-Network Luminescent Films Constructed Using Sulfur Quantum Dots and Lanthanide Complexes

“…With the rapid development of intelligence science, self-healing, tough, and stretchable materials have become highly desirable and have been attracting increasing attention for their promising application in stretchable sensors, health monitors, surface protection coatings, and so on. − Recently, great progresses have been achieved in developing self-healing hydrogels based on dynamic noncovalent interactions (hydrogen bonds, electrostatic interactions, metal coordination bonds, supramolecular interactions, and hydrophobic interactions), motivating various scientific and engineering innovations in the field of flexible devices. − However, the practical long-term application of synthetic hydrogels is susceptible due to their internal structural defects and fatigue fracture, even though their toughness could be improved by introducing multiple interactions. − On the one hand, lots of water molecules in the hydrogels can disturb the reconnection of dynamic bonds, impeding their further self-healing behavior . On the other hand, it is difficult to simultaneously enhance the mechanical strength and optimize the healing efficiency because these characteristics are contradictory. , Except for the above-mentioned two defects, endowing self-healing materials with photoluminescent (PL) property can promote and extend their applications under more complex working conditions, such as biosensors and optical switch. − …”

“…10−12 On the one hand, lots of water molecules in the hydrogels can disturb the reconnection of dynamic bonds, impeding their further selfhealing behavior. 13 On the other hand, it is difficult to simultaneously enhance the mechanical strength and optimize the healing efficiency because these characteristics are contradictory. 14,15 Except for the above-mentioned two defects, endowing self-healing materials with photoluminescent (PL) property can promote and extend their applications under more complex working conditions, such as biosensors and optical switch.…”