Modelling Microparticle Manufacture

Microparticles - 1 to 100 micrometer sized capsules - will enable cheap and precise single-cell analysis. Current research uses temperature-induced phase separation to efficiently fabricate polymer gel microparticles of desired shapes and sizes. To better understand this process, we develop several models of microscale phase separation of ternary fluids. A simple surface energy minimisation model describes possible equilibrium microparticle shapes. We then interrogate the dynamics of microparticle manufacture by combining a ternary Cahn-Hilliard model with surface tension- and buoyancy-driven Stokes flow. By simulating the model in three dimensions using the efficient Dedalus spectral code, we show that all physical effects - surface tension, fluid flow, and buoyancy - are necessary for microparticles to attain crescent configurations. Without fluid flow or buoyancy, microparticles consistently settle on spherical shell equilibria, in contrast to experiments. We then outline how varying surface energies, densities, viscosities, and concentrations can each influence microparticle manufacture, before concluding with a discussion of how fluid stresses drive microparticle evolution.