title: Theoretical investigation of a technique to produce microbubbles by a microfluidic T junction.
abstract: A microfluidic technique is proposed to produce microbubbles. A gaseous stream is injected through a T junction into a channel transporting a liquid current. The gas adheres to a hydrophobic strip printed on the channel surface. When the gas and liquid flow rates are set appropriately, a gaseous rivulet flows over that strip. The rivulet breaks up downstream due to a capillary pearling instability, which leads to a monodisperse collection of microbubbles that can be much smaller than the channel size. The physics of the process is theoretically investigated, using both full numerical simulation of the Navier-Stokes equations and a linear stability analysis of an infinite gaseous rivulet driven by a coflowing liquid stream. This stability analysis allows one to determine a necessary condition to get this effect in a T junction device. It also provides reasonably good predictions for the size of the produced microbubbles as obtained from numerical experiments.
authors.affiliation: Escuela Superior de Ingenieros, Universidad de Sevilla, Camino de los Descubrimientos s/n, E-41092 Sevilla, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: Herrada
authors.forename: A M
authors.initials: AM
authors.lastname: Gañán-Calvo
authors.forename: J M
authors.initials: JM
authors.lastname: Montanero