A Stretchy, Rubber-Like Energy Storage Device for Wearable Tech

Professor Jin Kon Kim and Dr. Keon-Woo Kim from the Department of Chemical Engineering at Pohang University of Science and Technology (POSTECH), in collaboration with Dr. Chanwoo Yang and Researcher Seong Ju Park from the Korea Institute of Industrial Technology (KITECH), have achieved a significant breakthrough in developing a small-scale energy storage device capable of stretching, twisting, folding, and wrinkling. Their research has been published in the esteemed electronic engineering journal, npj Flexible Electronics.

The advent of wearable technology has brought with it a pressing need for energy storage solutions that can keep pace with the flexibility and stretchability of soft electronic devices. Micro supercapacitors^*1 (MSCs) have emerged as a promising candidate for deformable energy storage, due to high-power density, rapid charging, and long cycle life. However, the fabrication of interdigitated electrode patterns capable of maintaining the energy storage performance under repeated stretching and twisting has remained a great challenge, because brittle materials like gold (Au) have been commonly used as an electrode. Meanwhile, though eutectic gallium-indium liquid metal (EGaIn) has high conductivity and deformability, a fine patterning of EGaIn is extremely difficult due to very high surface tension of EGaIn.

The research team successfully fabricated fine patterning, by using laser, of both EGaIn and graphene (serving as an active material) layers as on a stretchable polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene copolymer (SEBS) substrate. During laser ablation of EGaIn and graphene layers, the underlying stretchable SEBS substrate was not damaged, which maintained the flexibility of MSC device. The areal capacitance of the resulting MSC retains its original value even after stretching up to 1,000 cycles. Also, the fabricated MSCs operate stably under various mechanical deformations, including stretching, folding, twisting, and wrinkling (see the attached images).

This research was granted financial resources (National Creative Research Initiative Program) from the Ministry of Economy and Finance, Republic of Korea, and supported by the Industry-leading Core Production Technology Development Project of the Korea Institute of Industrial Technology.

Reference: Kim KW, Park SJ, Park SJ, et al. Deformable micro-supercapacitor fabricated via laser ablation patterning of Graphene/liquid metal. npj Flex Electron. 2024;8(1):18. doi: 10.1038/s41528-024-00306-2

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