Transparent, Highly Stretchable, Rehealable, Sensing, and Fully Recyclable Ionic Conductors Fabricated by One‐Step Polymerization Based on a Small Biological Molecule

Abstract

To date, various stretchable conductors have been fabricated, but simultaneous realization of the transparency, high stretchability, electrical conductivity, self-healing capability, and sensing property through a simple, fast, cost-efficient approach is still challenging. Here, α-lipoic acid (LA), a naturally small biological molecule found in humans and animals, is used to fabricate transparent (>85%), electrical conductivity, highly stretchable (strain up to 1100%), and rehealable (mechanical healing efficiency of 86%, electrical healing efficiency of 96%) ionic conductor by solvent-free one-step polymerization. Furthermore, the ionic conductors with appealing sensitivity can be served as strain sensors to detect and distinguish various human activities. Notably, this ionic conductor can be fully recycled and reprocessed into new ionic conductors or adhesives by a direct heating process, which offers a promising prospect in great reduction of electronic wastes that have brought acute environmental pollution. In consideration of the extremely facile preparation process, biological available materials, satisfactory functionalities, and full recyclability, the emergence of LA-based ionic conductors is believed to open up a new avenue for developing sustainable and wearable electronic devices in the future.features. [1][2][3][4] These conductors provide huge opportunities for promising applications of artificial muscles, skin sensors, biological actuators, stretchable displays, electronic eye cameras, intelligent robot arms, and others. [5][6][7][8][9][10][11] It was well known that the conventional electronic conductors are normally prepared from waferbased materials, which possess several drawbacks including fragility, rigidity, and low conductivity under large-scale deformations. [12] They cannot satisfy the demands of high stretchability, flexibility, durability, and stability. To achieve these criteria, strain engineering and nanocomposites are the two most adoptable strategies to fabricate stretchable conductors. In the first strategy, nonstretchable inorganic materials, such as silicon and metals, are geometrically patterned into buckled, serpentine structures on elastomeric substrates that renders the conductors excellent sensitivity and larger workable range of strain. [10,13,14] Nonetheless, most resultant conductors still show narrow range of strain from 20% to 70%, [15] and presents out-of-plane patterns that is difficult to encapsulate. Meanwhile, this strategy usually involves expensive and very complicated techniques, which greatly limits the further development of these conductors. Integrating conductive fillers into polymer matrix to produce nanocomposites used as stretchable conductors is the second strategy. [16] So far, various nanomaterials, such as carbon nanotubes, [17][18][19][20] carbon black, [21] graphene-based materials, [22,23] metal nanowires, and nanoparticles, [24,25] have been used as conductive fillers because of their unique mechanical and electrical properties. Although the robu...

Renewable Castor‐Oil‐based Waterborne Polyurethane Networks: Simultaneously Showing High Strength, Self‐Healing, Processability and Tunable Multishape Memory

“…Dang et al. synthesized a series of highly stretchable ionic conductors by constructing hierarchical networks containing disulfide bonds, which possess excellent mechanical healing efficiency, 86 % recovery (tensile strength in the range 47–152 kPa) after re‐healing for 14 h at 25 °C, and could be fully reprocessed into new conductors by a direct heating process [7a] . Methacrylate copolymers with dual sulfide–disulfide cross‐linked networks, developed by An et al., displayed rapid self‐healability for 0.5–30 min at room temperature [9a] .…”

Highly Strong and Transparent Ionic Conductive Hydrogel as Multifunctional Sensors

“…This result suggested that the hydrogels had shaped a stable network and exhibited predominant elastic solid performances. [ 33 ] The gradual augment of G ′ and G ′′ with the frequency increasing from 0.1 to 100 rad s −1 , which may on account of the relaxation effect of hydrogen bonds. [ 40 ] Besides, G ′ of the DN‐hydrogel with β‐CD 3.5% reached the highest.…”

Self‐Healing Soft Sensors: From Material Design to Implementation

“…Additionally, the expensive nanomaterials, relatively complicated and time‐consuming fabrication processes are also significant limiting factors facing these stretchable conductors. [ 46,47 ] These problems encouraged researchers to seek other directions, such as polymer blends and ionic conductors for preparing self‐healing sensing components.…”

“…It is worth mentioning that, although not defined explicitly as green sensing materials and devices, many reported examples are innately green and ecofriendly. [ 46,107,127,128 ] Nature has always been a source of inspiration for developing new functional materials. Therefore, turning to existing biological systems and materials that combine both degradability and self‐healing capabilities is highly attractive.…”