Tough, Self-Healing, and Conductive Elastomer ─Ionic PEGgel

Abstract

Ionically conductive elastomers are necessary for realizing human−machine interfaces, bioelectronic applications, or durable wearable sensors. Current design strategies, however, often suffer from solvent leakage and evaporation, or from poor mechanical properties. Here, we report a strategy to fabricate ionic elastomers (IHPs) demonstrating high conductivity (0.04 S m −1 ), excellent electrochemical stability (>60,000 cycles), ultrastretchability (up to 1400%), high toughness (7.16 MJ m −3 ), and fast self-healing properties, enabling the restoration of ionic conductivity within seconds, as well as no solvent leakage. The ionic elastomer is composed of in situ formed physically crosslinked poly(2-hydroxyethyl methacrylate) networks and poly-(ethylene glycol) (PEG). The long molecular chains of PEG serve as a solvent for dissolving electrolytes, improve its long-term stability, reduce solvent leakage, and ensure the outstanding mechanical properties of the IHP. Surprisingly, the incorporation of ions into PEG simultaneously enhances the strength and toughness of the elastomer. The strengthening and toughening mechanisms were further revealed by molecular simulation. We demonstrate an application of the IHPs as (a) flexible sensors for strain or temperature sensing, (b) skin electrodes for recording electrocardiograms, and (c) a tough and sensing material for pneumatic artificial muscles. The proposed strategy is simple and easily scalable and can further inspire the design of novel ionic elastomers for ionotronics applications.

A liquid-free conducting ionoelastomer for 3D printable multifunctional self-healing electronic skin with tactile sensing capabilities

“…Surprisingly, the breaking strength increased to 1.2 MPa, and the (f) Comparison of the LFCIg with previously studied materials in terms of recovery time and self-healing efficiency. 31,44,48,[54][55][56][57][58][59] The details are presented in Table S2 of the ESI. † (g) Self-healing process of ionogel.…”

“…(e) Resistance changes of LFCIg during the cutting and contacting process. (f) Comparison of the LFCIg with previously studied materials in terms of recovery time and self-healing efficiency 31,44,48,[54][55][56][57][58][59]. The details are presented in TableS2of the ESI.…”

Elastomeric polymers for conductive layers of flexible sensors: Materials, fabrication, performance, and applications

“…[ 284 ] In brief, an elastomeric active layer is sandwiched between two electrode layers to fabricate flexible resistive sensors. [ 285–287 ] Because of simple structure and straightforward measurement method, resistive pressure/strain sensors are the most commonly used. Tan et al.…”

“…[284] In brief, an elastomeric active layer is sandwiched between two electrode layers to fabricate flexible resistive sensors. [285][286][287] Because of simple structure and straightforward measurement method, resistive pressure/strain sensors are the most commonly used. Tan et al [288] fabricated a strain sensor based on TPU-boron nitride nanosheet (TPU-BNNS) membranes, which can be tightly bonded with the TPU fiber membranes deposited with graphene nanoribbon (GNR) nanonetworks, and then attached two copper foils to each of the exposed ends of the fiber membranes (Figure 7A).…”

High‐Toughness and High‐Strength Solvent‐Free Linear Poly(ionic liquid) Elastomers

“…The PIL-Zn prepared from halometallate ILs with supramolecular network structure exhibits high mechanical properties, including high mechanical strength (16.5 MPa) and good tensile properties (4220%). This provides significant advantages compared to nonionic elastomers, [38][39][40][41][42][43][44][45][46][47] ionic elastomers containing metal chloride, [14,[48][49][50][51][52][53][54] and reported PIL elastomers [22,55,56] (Figure 3f). Moreover, the corresponding calculated Young's modulus (157.49 MPa) and toughness (130.31 MJ m −3 ) are much higher than those previously reported (Figure 3g,h), further demonstrating their exceptional mechanical performance.…”