Experimental characterization of a silicone oil-in-water droplet generator based on a micro T-junction

This paper deals with the emulsion of two immiscible fluids in a micro T-junction. An opposed-flow micro T-junction obtained by means of square microchannels (with a side of 300 μm) fabricated in a pure fused glass chip has been used for the formation of silicone oil-in-water (O/W) droplets. The experimental results have been obtained by considering both pure deionized water and a mixture of deionized water and surfactant (Tween 20) as the continuous flow. The results shown in this paper highlight that the presence of surfactant, also in very small concentrations, is able to change drastically the flow patterns of the two-phase flow generated by the T-junction. Concentration in weight of Tween 20 between 1 and 2% in the continuous flow is able to promote highly monodispersed emulsions with low polydispersity, especially for low flow rate ratios between the dispersed and continuous phase flows. On the contrary, by avoiding the use of surfactant, a stratified flow is obtained. The experimental results obtained in this work have been used in order to link the depth ratio of the stratified flow and the non-dimensional length of the plugs in droplet-based flow to the flow rate ratio between the dispersed and continuous flows.