Physics of hard spheres experiment-2 (PHSE-2)

The Physics of Hard Spheres Experiment-2 (PH^ASE-2) seeks to answer fundamental questions about how model atoms change their behavior as more and more neighbors are moved into their neighborhood. The PH^ASE-2 experiment will use an enhanced microscope to observe colloidal particles crowded in a liquid phase make the transition to a solid phase. In the absence of gravitational masking, we can observe natural phase transitions, and the effects of aiding or frustrating these phase transitions. This allows us to gain an understanding of material behavior that lies at the core of how fundamental material properties manifest in the atomic world. When we increase the number of uniformly sized hard sphere particles in a volume or equivalently look at identical colloidal particles in a large number of sample cells spanning a range of concentrations (volume fractions), we see a fluid go from a liquid phase, to coexisting phases, to a crystalline phase, and with further crowding on earth to a glassy phase. While dendritic growth is not observed for hard spheres on earth, and the glass transition is, the opposite behavior is seen in experiments in microgravity. We intend to find out why by studying and actively manipulating specially coated particles that behave as hard spheres and therefore are only affected by configurational entropy. Choosing a particle size comparable to the wavelength of light selects the timescale of the experiment and permits us to observe model atoms with a microscope. Working in a size range that allows both microscopic and mesoscopic manipulation and control of the samples allows us to probe the essential features of the hard sphere disorderorder transition and the properties of the ordered solid phase that results.