Fabrication of monolayers of uniform polymeric particles by inkjet printing of monodisperse emulsions produced by microfluidics.

Emulsion solvent evaporation is a well-established method for generating microparticles from solutions of polymers in volatile organic solvents dispersed in an aqueous medium. Previous work has shown that this approach can also be used to deposit particles by inkjet printing where the particles are formed during the drying of a liquid ink on a substrate. The particle size distribution, however, was very broad. Here we demonstrate that inkjet printing of oil-in-water emulsions produced by microfluidics can generate micron-sized particles with a narrow size distribution (coefficient of variation <6%) and that these particles can self-assemble into ordered arrays with hexagonal packing. The conditions under which drops can be printed with a minimum of break up and coalescence of the oil droplets in the emulsion are explored. Factors affecting the size of the particles and the morphology of the deposit are described. This study uses polystyrene in dichloromethane as a model system, but the approach can be generalized to the production of structured and functional particles.