Article published in ACS Applied Materials & Interfaces, the top journal in the chemical materials field

"Low-toxicity, biocompatible liquid metal opens the door to ultraflexible wearable devices."
- Important research accomplishments about the release properties and toxicity of liquid metals, which are materials for next-generation electronic devices
- Provision of useful guidelines for the bio-device applications of liquid metals
Professor Koo, Hyung-jun's Group from the Department of Chemical and Biomolecular Engineering of SeoulTech (First author: Kim, Ji-hye from Master’s course) conducted systematic experiments about the release properties and toxicity of gallium-based liquid metals, and published a research article demonstrating their applicability to electrodes for wearable devices.

▲ Schematic diagram and plot showing the release of ions from liquid metal to aqueous solution and the result of the cytotoxicity experiment with the aqueous solution containing the released ions.
Liquid metals refer to metals that exist as liquids at room temperature due to their low melting point. They may flow like a liquid and have conductivity as high as other metals. Therefore, they are currently being extensively studied in the field of flexible electronic devices. Representative liquid metals include mercury and eutectic gallium-indium alloy (EGaIn).
The application of liquid metals to devices—particularly those used in biotechnology or those in contact with the human body—requires biocompatibility and toxicity studies. While the toxicity of the individual ions that make up liquid metals has been studied, the release properties of liquid metals themselves and their cytotoxicity have not yet been reported.

Professor Koo's group analyzed the concentration of ions released from EGaIn, a gallium-based liquid metal, into an aqueous solution. They found that the main released ions are determined by the surface tension of the atoms contained in the liquid metal, and that the ion concentration is proportional to the surface area and shape of the liquid metals and to the physical stimulus applied to them.
A cytotoxicity experiment was performed on three types of human cells to determine the biocompatibility of the EGaIn liquid metal. The results showed considerably low cytotoxicity, unless an external physical stimulus was applied.
Professor Koo's group provided fundamental and useful guidelines for the application of EGaIn liquid metal to bio-devices through their analysis of the liquid metal release into an aqueous solution and their cytotoxicity study.

Their article entitled "Cytotoxicity of Gallium-Indium Liquid Metal in an Aqueous Environment" was published in the May 1 online edition of ACS Applied Materials & Interfaces (IF 7.504), the top journal in the field of chemical materials that is published by the American Chemical Society.
The present study was supported by the Individual Basic Science & Engineering Research Program of the Ministry of Education, the Education Ministry, and the Challenging Nano-Material Technology Development Program of the Ministry of Science and ICT. The research project was conducted as a joint study with Professor Kim, Gyo-bum's group from Incheon National University and Dr. So, Ju-hui from the Korea Institute of Industrial Technology.