Owing to its low vapor pressure, low toxicity, high thermal and electrical conductivities, eutectic Ga-In (EGaIn) has shown a great potential for smart material applications in flexible devices, cooling in micro-devices, self-healing reconfigurable materials, and actuators. For such applications, EGaIn is maintained above its melting point, below which it undergoes solidification and complex phase separation. A scientific understanding of the structural and compositional evolution during thermal cycling could help further assess the application range of Ga and other low-melting-point fusible alloys. Here, we use an integrated suite of cryogenically-enabled advanced microscopy & microanalysis to better understand phase separation and (re)mixing processes in EGaIn. We reveal an overlooked thermal-stimulus-response behavior for frozen mesoscale EGaIn at cryogenic temperatures, with a sudden volume expansion observed during in-situ heat-cycling, associated with the immiscibility between Ga and In during cooling and the formation of metastable Ga phases. These results emphasize the importance of the kinetics of rejuvenation, and open new paths for EGaIn in sensor applications.
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