Generation of uniform photonic balls by electrohydrodynamic atomization

Abstract

We prepared uniform-sized suspension droplets with polystyrene (PS) beads by electrohydrodynamic atomization (EHDA) and subsequently colloidal crystals by evaporation-induced self-assembly (EISA) in the droplets. Electrospray of the aqueous suspension under a carbon dioxide sheath flow was conducted to study the feasibility of monodisperse droplet generation. For optical applications, spherical PS colloidal crystals were prepared in the size range of 10~20㎛ with PS beads in size range 200~350nm, which was measured by dynamic light scattering. The colloidal crystal possessed closed packed hexagonal domains in spherical shape. The size and morphology of colloidal crystals were imaged by SEM. In the present study, the suspension droplets were dispersed in silicon oil or mineral oil that has appropriate density and viscosity to form stable spherical-shaped colloidal crystals.