Authors: J.M. Gordillo, E. Castro-Hernandez, W. van Hoeve, F. Campo-Cortes, D. Lohse
Affilation: Universidad de Sevilla, Spain
Pages: 321 - 324
Keywords: drug delivery, ultrasound contrast agents, colloidal emulsions, cleaning technologies
Here we propose two different ways to generate either monodisperse microemulsions or monodisperse microbubbles. With the first of these techniques a jet is formed with the same type of cone-jet geometry predicted by the numerical results by Suryo and Basaran, Phys. Fluids, 18, 082102, (2006). We show that, through this simple method, concentrated emulsions composed of micron-sized drops with a narrow size distribution can be generated. Both numerical simulations and theory predict both the jet shapes and drop sizes, in very good agreement with experiments. The second of these techniques uses PDMS-based flow-focusing microfluidic devices. We show that monodisperse microbubbles with diameters below one-tenth of the channel width can be produced in low viscosity liquids thanks to a strong pressure gradient in the entrance region of the channel. In this new regime bubbles are generated at the tip of a long and stable gas ligament whose diameter is substantially smaller than the channel width. The experimental results for the bubble diameter as function of the control parameters are accounted for by a scaling theory in excellent agreement with experiments. These monodisperse bubbles, stabilized with a phospholipid cover, possess the appropriate diameter for therapeutical applications ($d_b simeq 5$,$mu,m$) or cleaning technologies and at a production rate exceeding $10^5$ Hz.