Long-time observation of near-critical spinodal decomposition of colloid-polymer mixtures in microgravity
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We investigate liquid-gas phase separation near the critical point of colloid-polymer mixtures aboard the International Space Station, as part of the BCAT3 and BCAT4 experiments. In this microgravity environment, the higher-density liquid phase does not sink beneath the lower-density gas phase, as it does on the surface of the earth. Instead, we can observe the patterns formed during spinodal decomposition, using time-lapse photography for days to weeks, while previous experiments have been limited to observations of minutes to hours. We give a primer on phase separation and detail our sample preparation procedures. We also describe the specific innovations in our photography procedures made by a number of astronauts on orbit, demonstrating the importance of a manned microgravity laboratory to our investigation. Copyright 2009 by Peter J. Lu.