The effect of the hydrophobicity of microchannels and components in water and oil phases on droplet formation in microchannel water-in-oil emulsification

Abstract

The effects of the hydrophobicity of silicon microchannels and components in the oil and water phases in the production of monodispersed water-in-oil (W/O) emulsions by microchannel emulsification was investigated. Several types of silane coupler reagents were applied to make the microchannel hydrophobic. The hydrophobicity of the surface was evaluated by contact angle measurements. Hexane, decane and oleic acid were used as the oil phase, and pure water and sucrose solution were used as the water phase. Tetraglycerol polyricinoleate, sodium bis(2-ethylhexyl) sulfosuccinate and sorbitan fatty acid esters were used as surfactants. The contact angle of a water droplet on the modified silicon microchannel plate in an oil phase was found to be dependent on the composition of the oil phase, the surfactant type and the silane coupler reagent used for surface modification. When the contact angle was greater than 120°, monodispersed water droplets were formed and the geometric standard deviation was below 1.06. The average droplet size varied from 17 to 23 μm, and was affected by the characteristics of the surfactant and the viscosities of the water and oil phases.