Materialia, 2019, vol 8pp. 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.