Criteria for drop generation in multiphase microfluidic devices

• Published in: Physical review. E Vol. 95; no. 6-1; p. 063103
• Main Authors: Buttacci, Joseph D, Loewenberg, Michael, Roberts, Christine C, Nemer, Martin B, Rao, Rekha R
• Format: Journal Article
• Language: English
• Published: United States 01.06.2017
• ISSN: 2470-0053
• DOI: 10.1103/PhysRevE.95.063103

A theory is presented for the transition between the coflowing and the drop-generation regimes observed in microfluidic channels with a rectangular cross section. This transition is characterized by a critical ratio of the dispersed- to continuous-phase volume flow rates. At flow-rate ratios higher than this critical value, drop generation is suppressed. The critical ratio corresponds to the fluid cross section where the dispersed-phase fluid is just tangent to the channel walls. The transition criterion is a function of the ratio of the fluid viscosities, the three-phase contact angle formed between the fluid phases and the channel walls, and the aspect ratio of the channel cross section; the transition is independent of interfacial tension. Hysteretic behavior of drop generation with respect to the flow-rate ratio is predicted for partially wetting dispersed-phase fluids. Experimental data are consistent with this theory.