A Microphase‐Separated Design toward an All‐Round Ionic Hydrogel with Discriminable and Anti‐Disturbance Multisensory Functions

Abstract

Stretchable ionic hydrogels with superior all‐round properties that can detect multimodal sensations with high discriminability to decouple multiple stimuli and high robustness against external disturbances are highly required for artificial electronic skin applications. However, some of the critical material parameters exhibit intrinsic tradeoffs with each other for most ionic hydrogels. Here, we demonstrate a microphase‐separated hydrogel design by combining three strategies: (1) the use of a low crosslinker/monomer ratio to obtain highly entangled polymer chains as the first network; (2) the introduction of zwitterions into the first network; (3) the synthesis of an ultrasoft polyelectrolyte as the second network. This approach creates an all‐round elastic ionic hydrogel with a skin‐like low Young's modulus (< 60 kPa), large stretchability (> 900%), high resilience (> 95%), low hysteresis (< 5%), unique strain‐stiffening behavior, excellent fatigue tolerance, high ionic conductivity (> 2.0 S/m), and anti‐freezing capability, which were not achieved with previous ionic hydrogels. These comprehensive properties allow the ionic hydrogel to operate as a stretchable multimodal sensor that can detect and decouple multiple stimuli (temperature, pressure, and proximity) with both high discriminability and sensitivity. It also shows strong sensing robustness against strains and temperature perturbations. The ionic hydrogel sensor exhibits great potential for intelligent electronic skin applications such as reliable health monitoring and accurate object identification.This article is protected by copyright. All rights reserved

Multifunctional Polyoxometalates‐Based Ionohydrogels toward Flexible Electronics

“…Ionic liquid-based gels (ILGs), denoting polymer networks swollen with ionic liquids (ILs) as the continuous and/or dispersed phases-have attracted considerable attention due to their unique properties, including inherently strong stretchability comparable to biotissues, favorable viscoelasticity, self-adhesive, excellent thermal and electrochemical stability, and high ionic conductivity. [12][13][14][15] Various methodologies, such as incorporation of energy dissipation, [16,17] establishment of double and triplenetwork, [18][19][20] formation of physical and chemical crosslinks, [21,22] interpenetration of polymer network, [23][24][25] design of topoarchitected polymer networks, [26,27] incorporation of iondipole interactions, [28,29] construction of slide ring networks, [30,31] incorporation of particles, [32,33] implementation of solvent exchange, [34,35] and manipulation of phase separation, [36][37][38][39] have been successful to develop ILGs with enhanced toughness. Despite these advancements, the realization of multifunctional ILGs remains a significant challenge.…”

The design of multi-functional ionic hydrogels with anti-freezing, temperature response and luminescence properties

“…Thus, an anti-freezing capability is a desirable property in ionic hydrogels so they can be applied under harsh climatic conditions. 16…”

Phase Transition-Induced Nanohydrogel Electrolytes with High Tensile Strength, Robust Adhesion, and Superior Antifreezing

“…However, some inevitable limitations prevent their application in all-in-one supercapacitors. First, the mechanical weakness of hydrogel electrolytes often affects the safety, stability, and reliability of wearable electronics that can accommodate large strains of multiple body movements . Second, the limited interface interactions between hydrogel electrolytes and conductive polymer electrodes cause the electrode material to easily fall off and severely reduce the service reliability of all-in-one supercapacitors .…”

“…First, the mechanical weakness of hydrogel electrolytes often affects the safety, stability, and reliability of wearable electronics that can accommodate large strains of multiple body movements. 2 Second, the limited interface interactions between hydrogel electrolytes and conductive polymer electrodes cause the electrode material to easily fall off and severely reduce the service reliability of all-in-one supercapacitors. 3 Third, hydrogel electrolytes have insufficient freezing resistance, leading to mechanical and electrical conductivity loss when exposed to harsh conditions.…”