Recent Progresses in Liquid‐Free Soft Ionic Conductive Elastomers^†

Abstract

Comprehensive Summary With the rapid growth of soft electronic and ionotronic devices such as artificial tissues, soft luminescent devices, soft robotics, and human‐machine interfaces, there is a demanding need to accelerate the development of soft ionic conductive materials. To date, the first‐generation ionotronic devices are mainly based on hydrogels or ionogels. However, due to their intrinsic drawbacks, such as freezing or volatilization at extreme temperatures, and the leakage problem under external mechanical forces, the reliability of ionotronic devices under harsh conditions remains a great challenge. The advent of liquid‐free ionic conductive elastomers (ICEs) has the potentials to solve the issues related to the gel‐type soft conductive materials. The free ions shuttling within the ion‐dissolvable polymer network enable liquid‐free ICEs to exhibit unparalleled ionic conductivity and elasticity. Moreover, by tuning the composition and structure of the polymeric network, it is also feasible to integrate other desirable properties, such as self‐healing ability, transparency, biocompatibility, and stimulus responsiveness, into liquid‐free ICE materials. In this review, we summarize the design strategies of recently reported liquid‐free ICEs, and further explore the methods to introduce multifunctionality, which originate from the rational molecular design and/or the synergy with other materials. Moreover, we highlight the representative applications of liquid‐free ICEs in soft ionotronics. It is believed that liquid‐free ICEs might provide a unique material platform for the next‐generation ionotronics.

Hierarchical Sponge‐Hydrogel Hybrid Structures with Robust Interfaces†

“…Synthetic polymer sponge materials, such as polyurethane (PU), polydimethylsiloxane (PDMS), latex, ethylene‐vinyl acetate (EVA) and polyethylene (PE), etc ., are featured attractive characters, such as reversible compressibility, mechanical robustness, high porosity and large pore volume, as well as superior capacity for liquid absorption. [ 1‐6 ] Most recently, functional sponge materials have found applications in a variety of fields, including electrodes, [ 7 ] batteries, [ 8 ] supercapacitors, [ 9 ] biomedical scaffolds [ 10 ] and solar vapor absorbents. [ 11 ] However, these synthetic polymer sponge materials are relatively hydrophobic, together with their intrinsic large mesh interstices.…”

Skin-inspired gradient ionogels induced by electric field for ultrasensitive and ultrafast-responsive multifunctional ionotronics

“…[1][2][3][4][5][6][7][8] Meanwhile, high-performance so ionic conductors with high ionic conductivity, excellent stretchability/ compressibility, and good transparency are also urgently needed. [9][10][11][12] Among the reported so ionic conductors, hydrogels are thought to be good candidates due to their optical transparency, good stretchability, and desirable ionic conductivity. [13][14][15][16][17][18] Nevertheless, narrow operating temperature and low water retention ability, especially the problems of freezing at low temperatures and the rapid evaporation of water at high temperatures, limit the wide applications of so ionotronics based on hydrogels.…”

A Fully Self‐Healing and Highly Stretchable Liquid‐Free Ionic Conductive Elastomer for Soft Ionotronics

“…[23] The advent of liquid-free ionic conductive elastomers (ICEs) suggests the potential to address the aforementioned issues associated with gel-type conductive materials. [24][25][26] In general, three different strategies have been proposed to construct liquid-free ICEs, [27] including salt-doping elastomers, [28,29] polymerizable deep eutectic solvent based elastomers, [30,31] and single-ion conductive elastomers. [18,32] Among these, salt-doping elastomers have been widely adopted due to their simplicity and efficiency.…”