Chinese scientists have successfully developed elastomeric conductors with high environmental tolerance

On October 3, 2022, Professor Huaiping from Hefei University of Technology and the team of Academician Yu Shuhong of the University of Science and Technology of China published an article titled “Highly compressible and environmentally adaptive conductors with high-tortuosity interconnected cellular” in the journal Nature Synthesis architecture” research results.

The research team developed a synthesis method that combines “orientation assembly and programmed polymerization” to achieve universal adaptation of compression-resistant elastomeric conductor materials with high curvature cellular cross-linking network structure and multiple extreme environmental tolerances, providing a material solution for the construction of flexible wearable devices for complex environmental applications. The corresponding authors of the paper are Conghuai Ping and Yu Shuhong; The first authors are Wang Yangyu and Qin Haili.

Conductive hydrogels have important applications in the fields of flexible wearable electronic devices, bioelectronic devices and soft robots due to their unique conductive properties, adhesion to complex curved surfaces and intelligent response to mechanical stimulation. Due to the lack of effective structural design and synthesis strategies, the fatigue resistance of current synthetic hydrogels is still much lower than that of natural biological tissues, which seriously limits practical applications. Inspired by the honeycomb structure biomaterials in nature, scientists have developed a series of porous carbon conductive materials with excellent compression resistance. However, due to their limited composition and imperfect structure, these materials are less adaptable to the environment and can usually only maintain good mechanical properties under natural conditions. Especially under repeated compression conditions, the problems of permanent decline in the mechanical strength of materials and a sharp increase in residual strain are still very serious. Therefore, there are still great challenges in how to accurately regulate the honeycomb grade structure across the scale, rationally design the elastic components, and continuously approach the theoretical limits of the mechanical elasticity and fatigue resistance of the material, so as to achieve the development of highly environmentally adaptable elastic materials.

Recently, Hefei University of Technology from Professor Huai Ping and Academician Yu Shuhong of the University of Science and Technology of China based on the development of “nano-primitive assembly collaborative in situ polymerization” strategy to regulate the structure and function of polymer networks based on the research basis (Angew. Chem. Int. Ed. 2022, e202209687; Nano Lett. 2022,22, 1433-1442; Nat. Commun. 2021, 12, 4297; Adv. Mater. 2019, 31, 1900573; Nat. Commun. 2018, 9, 2786), proposing a synthesis method that combines “orientation assembly and programmed polymerization”, through the stratigraphic, supramolecular scale, mesoscopic scale and nanomicroscale fine regulation of water molecule phase transition, interface polymerization, nanowire assembly cellular network curvature and cellular sidewall cross-linking structure from the molecular, supramolecular scale, mesoscopic scale and nano-microscale, resulting in the effect of “nanostructure unit orientation assembly – phase change induced distortion – polymerization stability structure”, and realizing a variety of anti-fatigue with anisotropic and highly curved endoplasmic reticulum structural characteristics, Compression-resistant conductive hydrogel is universally fitted. By further in situ crosslinking polymer chains, oily hydrogels rich in hydrophilic/lipophilic interpermeability network structures exhibit excellent mechanical and sensing behavior in a variety of organic solvents and at low temperatures.

Figure 1: Schematic diagram of the synthesis of a compression-resistant conductive hydrogel.

Figure 2: Mechanical properties of a compressive conductive hydrogel.

Thanks to the grade cellular network structure and concrete-reinforced composition, the synthetic hydrogel exhibits excellent compressive properties and fatigue resistance. Under 50% compression strain, 30,000 consecutive compressions produce only 1.5% irreversible deformation, which can still maintain about 80% of the mechanical strength. It is worth noting that the material achieves an unprecedented underwater compression elasticity of the hydrogel system, and there is no residual strain generation after 50,000 consecutive compressions under 50% underwater deformation. Based on the system’s unique responsiveness to mechanical deformation and highly elastic resilience, the hydrogel is capable of sensitively detecting the direction and velocity of material movement and can also be used as an underwater pressure sensor to sense human movement underwater.

Figure 3: Sensing properties of a compressive conductive hydrogel.

Figure 4: Synthesis and properties of oil-based hydrogels that are highly environmentally tolerant.

In order to solve the problem of low service performance of hydrogels in special environments such as solvents, the research group further proposed the organic hydrogel strategy, through in situ polymerization reaction in the hydrogel network composite lipophilic polymer, to build a unique lipophilic hydrophilic polymer chain interpenetration network structure, to achieve the hydrogel in the organic solvent and low temperature and a variety of harsh environments still maintain excellent flexibility and compression resistance.

This research provides a general method for the development of high-performance flexible conductive soft materials that can be prepared on a simple scale and integrated in a large area, and has great application potential in the field of building flexible wearable electronic devices for applications in extreme environments. The research work has been funded by the National Natural Science Foundation of China, the National Key Research and Development Program, the Special Fund for Basic Scientific Research Business Expenses of Central Universities, the Collaborative Innovation Project of Anhui Universities, and the Natural Science Foundation of Anhui Province. (Source: Science Network)

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