In the movie "Terminator," the liquid metal robot impressed audiences with its ability to change form. The eutectic gallium indium (EGaIn) spherical liquid metal nanoparticles (NPs) have similar deformability, transforming into gallium oxide hydroxide (GaOOH) microrods in water. This peculiar phenomenon has drawn much attention from researchers due to its unique properties and wide applications in fields including biomedicine, catalyst, and photonics. Nevertheless, the mechanism of this process remains unrevealed.

Recently, the mechanism of Eutectic gallium indium (EGaIn) nanoparticles’ (NPs) shape transformation has been studied in detail by the research group of Professor Jian Ye, School of Biomedical Engineering, Shanghai Jiao Tong University. Using sophisticated experimental design and a variety of characterization methods, the whole shape transformation process of EGaIn NPs is investigated via monitoring the change of NPs’composition and morphology. Gallium (Ga) element in EGaIn NPs can be oxidized to form gallium oxide, which further reacts with water to generate micrometer‐sized GaOOH crystals. This chemical variation occurs gently at room temperature and is accelerated by heating. With continuous consumption of Ga element, indium condenses to form individual NPs. Deep understanding of the mechanism of EGaIn NPs’ shape transformation would provide more approaches to control the surface and bulk properties of NPs for potential applications in various fields including soft robotics, wearable devices, and nanomedicine.

Additionally, this work proposed a strategy to prevent Ga from oxidization by using negatively-charged molecules. The promising approach to minimize the oxidation of active Ga and its alloys is capable to maintain the excellent native properties of LMs such as fluidity and conductivity at the nanoscale. A better understanding of the mechanism of EGaIn deformation provides further perspectives for the utilization of Ga-based NPs in related research fields such as nanomedicine, catalyst, soft robotics, and wearable devices. The results entitled“Shape Transformation Mechanism of Gallium-Indium Alloyed Liquid Metal Nanoparticles” were published in Advanced Materials Interfaces.

This study was conducted by the research group of Professor Jian Ye, School of Biomedical Engineering and the research group of Professor Jianbo Wu, School of Materials Science and Engineering, Shanghai Jiao Tong University. Doctoral students Jing He and Fenglei Shi contributed equally to this work. This study was supported by the National Natural Science Foundation of China, the Science and Technology Commission of Shanghai Municipality, Innovation Research Plan supported by Shanghai Municipal Education Commission, the 111 Project, Shanghai Jiao Tong University, and the fund from Center of Hydrogen Science and Joint Research Center for Clean Energy Materials at Shanghai Jiao Tong University, and Shanghai Key Laboratory of Gynecologic Oncology.

Original paper link: https://doi.org/10.1002/admi.202001874