A Transparent, Self‐Healing, Highly Stretchable Ionic Conductor

Abstract

Self-healing materials can repair damage caused by mechanical wear, thereby extending lifetime of devices. A transparent, self-healing, highly stretchable ionic conductor is presented that autonomously heals after experiencing severe mechanical damage. The design of this self-healing polymer uses ion-dipole interactions as the dynamic motif. The unique properties of this material when used to electrically activate transparent artificial muscles are demonstrated.

Recent Applications of Ionic Liquids in the Sol-Gel Process for Polymer–Silica Nanocomposites with Ionic Interfaces

“…Based on this idea, the use of ILs/PILs was demonstrated in many different polymer systems, such as: block copolymer/IL-based functional soft materials presenting spontaneous repair damage by light illumination, driven by a reversible gel-sol-gel transition cycle with a reversible association/fragmentation of the polymer network [151]; IL-modified epoxy resin thermoset with self-healing ability for surface abrasion damage, where the viscoelastic recovery and healing ability of the damaged surface increases with increasing IL content (up to~12 wt %) [152]; polymer/IL-based transparent, self-healing, highly stretchable ionic conductor, used to electrically activate transparent artificial muscles, that autonomously heals using ion-dipole interactions as the dynamic motif [153]; ionically cross-linked poly(acrylic acid) (PAA) and poly-(triethyl(4-vinylbenzyl)phosphonium chloride) networks presenting a salinity dependent swelling behavior, allowing them to self-heal in low and physiologically relevant salt concentrations for biomedical area [154]; or converting bromobutyl rubber into ionic imidazolium bromide reversible ionic associates, presenting physical cross-linking ability, which facilitates the healing processes by temperature-or stress-induced rearrangements, thereby enabling a fully cut sample to retain its original properties after the self-healing process [155]; just to mention a few.…”

Deformable and Transparent Ionic and Electronic Conductors for Soft Energy Devices

“…[231,232] Cao et al reported highly self-healing STIC using ion-dipole interactions. [43] The ionic conductor composed of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) as polymer matrix and 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMIOTf) as the ionic liquid shows a transmittance of 92% and can sustain a stretchability of 5000% while maintaining a high ionic conductivity of 10 −4 S cm −1 (Figure 19a,b). The presence of the reversible ion-dipole interactions impart self-healing properties to the STIC.…”

“…Hydrogel [141] Polyacrylamide, LiCl 90 800% -Ionic cable, axion Hydrogel [42] Polyacrylamide, LiCl 98 1000% -Touch panel Ionogel [43] PVDF-co-HFP 92 5000% 10 −4 S cm…”

“…Self-healing property of STIC is another advantage of soft energy devices. For example, polar polymer networks cross-linked with high ionic strength salt have been demonstrated as stretchable/ transparent/self-healing ionic conductors by using the dynamic bond formed by ion-dipole interactions [43] or hydrogen bonding interactions. [44,45] This entirely new, out-of-the-box approach to using STIC in electronic devices has gained considerable attention in the last two years, despite its nascent stage of development.…”

Self-Healing and Damage Resilience for Soft Robotics: A Review

“…Since multifunctional materials that bridge functional partitions drive innovation in the soft robotics field, it is worth pointing out how the self-healing materials discussed in the previous sections could continue to break down functional barriers. Recently, Cao et al (2017b) demonstrated the use of high-resistive, ionic, self-healing hydrogels as DEA electrodes, showing how work toward improving self-healing ionic hydrogels is also improving damage resilience in soft robotic actuation. Likewise, DEAs have also been used as sensory components in soft electronics (Iskandarani and Karimi, 2012;Xu et al, 2016), so progress made toward fault-tolerant and self-healing DEAs can also be applied to soft sensors and electronics.…”