A phase diagram of morphologies for anisotropic particles sculpted from emulsions.

ABSTRACT

HYPOTHESIS: A micron-scale oil-in-water emulsion droplet frozen in the presence of surfactants can be induced to eject the crystallizing solid from its liquid precursor. This dynamic process produces highly elongated solids whose shape depends critically on the rate of crystallization and the interfacial properties of the tri-phase system. EXPERIMENT By systematically varying the surfactant concentration and cooling protocol, including quenching from different temperatures as well as directly controlling the cooling rate, we map out the space of possible particle morphologies as a function of experimental control parameters. These results are analyzed using a non-equilibrium Monte Carlo model where crystallization rate and interfacial energies can be specified explicitly. FINDINGS: Our model successfully predicts the geometry of the resulting particles as well as emergent phenomena including how the particle shape depends on nucleation site and deformation of the precursor droplet during crystallization.