Solidification and melting phase change behavior of eutectic gallium-indium-tin

• Published in: Materialia 2019-12, Vol.8, p.100512, Article 100512
• Main Authors: Koh, Amanda, Hwang, Wonseok, Y. Zavalij, Peter, Chun, Seth, Slipher, Geoffrey, Mrozek, Randy
• Format: Article
• Language: English
• Subjects: Galinstan; Liquid metal; Phase change; Rheology; Stretchable electronics
• ISSN: 2589-1529; 2589-1529
• DOI: 10.1016/j.mtla.2019.100512

The room-temperature liquid metal alloy of gallium, indium, and tin (galinstan) has been studied as a deformable conductive element for stretchable electronics and soft robotics. While these applications are predicated on the soft and conformable behavior of galinstan, little work has been done to understand the solidification of the liquid metal in order to fully identify its operational range and that of devices using it. In this paper, the solidification and melting of galinstan is studied in bulk through rheology, x-ray scattering, and differential scanning calorimetry. It is determined that there is a gap of 20 degrees between solidification of galinstan at around -10°C and melting at 10°C. Crystallinity is observed below -10°C, suggesting ordering of the gallium, indium, and tin phases which is unstable through repeated solidify-melt cycles and possibly rearranges in structure below -30°C. Dispersions of galinstan in PDMS remain soft below -20°C while galinstan channels in PDMS appeared to solidify at length scales down to 500µm. Overall, galinstan can offer “liquid-like” performance down to -10°C however, at lower temperatures, solidification can occur at temperature and time that is dependent on the dispersion/ confinement state. If solidification occurs, galinstan must be heated substantially to regain its “liquid-like” performance. [Display omitted] Galinstan, as a liquid metal, is a deformable and stretchable conductor at and above room temperature. To understand the behavior of galinstan below room temperature, the rheological, melting, and crystalline properties of the liquid metal are explored in bulk and in PDMS composites. Solidification and crystallization was observed at -10°C while melting required further heating to 10°C.