Tough, Self-Healing,\nand Conductive Elastomer Ionic\nPEGgel

Abstract

Ionically conductive elastomers are necessary for realizing\nhuman–machine\ninterfaces, bioelectronic applications, or durable wearable sensors.\nCurrent design strategies, however, often suffer from solvent leakage\nand evaporation, or from poor mechanical properties. Here, we report\na strategy to fabricate ionic elastomers (IHPs) demonstrating high\nconductivity (0.04 S m^–1), excellent electrochemical\nstability (>60,000 cycles), ultra-stretchability (up to 1400%),\nhigh\ntoughness (7.16 MJ m^–3), and fast self-healing properties,\nenabling the restoration of ionic conductivity within seconds, as\nwell as no solvent leakage. The ionic elastomer is composed of in\nsitu formed physically cross-linked poly(2-hydroxyethyl methacrylate)\nnetworks and poly(ethylene glycol) (PEG). The long molecular chains\nof PEG serve as a solvent for dissolving electrolytes, improve its\nlong-term stability, reduce solvent leakage, and ensure the outstanding\nmechanical properties of the IHP. Surprisingly, the incorporation\nof ions into PEG simultaneously enhances the strength and toughness\nof the elastomer. The strengthening and toughening mechanisms were\nfurther revealed by molecular simulation. We demonstrate an application\nof the IHPs as (a) flexible sensors for strain or temperature sensing,\n(b) skin electrodes for recording electrocardiograms, and (c) a tough\nand sensing material for pneumatic artificial muscles. The proposed\nstrategy is simple and easily scalable and can further inspire the\ndesign of novel ionic elastomers for ionotronics applications.