(89a) Emulsification with Micro-Engineered Devices

The preparation of emulsions with conventional technologies requires tremendous energy inputs of which the majority is lost in heat generation. This is a direct consequence of the high shear rates, necessary for droplet breakup. Recently, microstructured devices have gained interest for applications in emulsion fabrication. This originates from the length scale of microstructures being comparable to desired droplet sizes. As such, droplet formation is strongly controlled and requires less energy. By using several micro engineered devices, mono-disperse emulsions were fabricated. First, cross flow membrane emulsification with well defined membranes is described. This method relies on the shear induced droplet detachment from a pore through which the dispersed phase is fed. Membrane surfaces that are not wetted by the dispersed phase are needed for this. Besides, the drop formation at a given pore influences the cross flow profile locally and thus the drop formation at nearby pores. Even for very uniform pore size distributions, relatively polydisperse emulsions were obtained. This was demonstrated by using different membranes with different pore sizes and geometries. Secondly, we studied emulsification in a porous channel where the continuous phase is fed through the porous walls of the channel. The continuous phase breaks up a jet of liquid into discrete drops. This method yields, as the flow focusing method, monodisperse emulsions. The size of the droplets is mainly determined by the radius of the channel.