Scholars have developed new liquid metal materials with both tensile and airtight properties

Recently, the team of Professor Deng Tao and the team of Shang Wen, associate researcher of the School of Materials Science and Engineering of Shanghai Jiao Tong University, solved the problem that traditional packaging materials cannot simultaneously balance stretchability and high air tightness by constructing liquid metal flexible sealing composites supported by micron glass ball arrays. The study was published Feb. 3 in Science.

The research concept diagram is from the research group

In recent years, the intelligence of human society has led the rapid development of flexible wearable devices. High-performance sealing materials prevent the ingress of damaging gases/liquids from the outside and the loss of active substances inside, which is essential for the long-term stable operation of flexible devices. However, existing encapsulation materials cannot balance sealing performance and stretchability at the same time. For example, metal and ceramic thin-film encapsulation materials have good air tightness, but do not have stretchability; Flexible elastomer packaging materials have excellent stretchability, but poor air tightness; The stretchability and sealing performance of traditional metal, ceramic and elastomer composite packaging materials are often mutually restricted, which cannot meet the reliable packaging requirements of advanced flexible devices.

In response to this challenge, the research team designed and prepared a composite packaging material based on liquid metal, compounded the common liquid metal gallium indium eutectic alloy (EGaIn) with an elastomer material, and cleverly used the micron glass sphere array as a support to prevent the encapsulation material from collapsing during deformation and causing the attenuation of sealing performance, and developed a highly gas-tight, stretchable packaging material that can integrate wireless communication functions, and its oxygen transmission coefficient is measured to be 5.0×10-23 m2/(s Pa). Close to metallic aluminum (Al), more than 8 orders of magnitude lower than traditional silicone elastomer materials.

Shen Qingchen, the first author of the paper and Ph.D. of Shanghai Jiao Tong University, introduced that the research team applied the liquid metal sealing composite material to package and perform tests on stretchable lithium-ion batteries based on aqueous electrolytes and found that in the natural unstretched state, the reversible capacity of the encapsulated lithium-ion battery was 105.5 mAh/g, and after 500 charge-discharge cycles, it could still maintain 72.5% of the initial capacity, while the traditional elastomer-encapsulated battery completely failed after about 160 cycles. Under the state of 20% tensile strain, the battery capacity of the liquid metal composite package can still be maintained at 105.0 mAh/g, and its constant current charge and discharge curve and corresponding capacity remain almost unchanged in the deformation state such as tensile, bending, and twisting. This shows that such devices have great potential as energy storage components in stretchable electronics.

In addition, the research team also found that liquid metal encapsulation composites also have excellent sealing effect against common organic solvents such as ethanol, which is expected to provide a new and reliable solution for thermal management of flexible electronic devices.

Dr. Qingchen Shen, Modi Jiang, Ruitong Wang, Kexian Song, and Man Hou Vong, Department of Chemical and Biomolecular Engineering, North Carolina State University, are co-first authors of the paper, Professor Deng Tao and Associate Researcher Wen Shang, Professor of School of Materials Science and Engineering, Shanghai Jiao Tong University, Michael D. Dickey, Professor of Department of Chemical and Biomolecular Engineering, North Carolina State University, and Dr. Wang Jun, Dr. Wang of A123 System R&D Center, are co-corresponding authors of the paper. (Source: Liu Runan, China Science News)

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