Effective pressure and bubble generation in a microfluidic T-junction

Abstract

To improve the existing trial-and-error process in designing a microfluidic T-junction, a systematic study of the geometrical (mainly the channel length) effects on the generated bubbly/slug flow was conducted to figure out basic design guidelines based on experimental and theoretical analyses. A driving system with dual constant pressure sources, instead of the commonly used dual constant volume-rate sources (such as two syringe pumps), was chosen in this study. The newly proposed effective pressure ratio (P(e)*) has revealed its advantages in excluding the surface tension effect of fluids. All the data of generated bubbly/slug flow for a given geometry collapse excellently into the same relationship of void fraction and effective pressure ratio. This relationship is insensitive to the liquid viscosity and the operation range is strongly affected by the geometrical effect, i.e., the channel length ratio of downstream to total equivalent length of the main channel in a T-junction chip. As to the theoretical design and analysis of gas-liquid-flow characteristics in a microfluidic T-junction, which is still sporadic in the literature, the proposed semi-empirical model has successfully predicted the operation boundaries and the output flow rate of bubbly/slug flow of different investigated cases and demonstrated its usability.

A novel technology: microfluidic devices for microbubble ultrasound contrast agent generation

“…1a) [30,36,80,99,101]. The gas phase tip enters the liquid channel, and then, the gaseous protrusion elongates in the liquid channel and is eventually broken into bubbles under the shear force of the liquid and the resultant pressure gradient [30,72,98].…”

Disintegration and conveyance of dielectric barrier discharge-generated micro-plasma ball under water

“…As shown in Figure 2, the gas penetrates into the plastic tube and forms a cylindrical stream of gas. After that, a bubble begins to form after it splits from its tip, which is controlled by inertia, viscosity, surface tension and gas-liquid flow rate [8][9][10]. In this study, helium gas was used as carrier gas because of its stable ionization.…”

Novel on-demand droplet generation for selective fluid sample extraction

“…The protrusion of the dispersed phase is then sheared by the continuous phase into a droplet (Figures 3). The shearing of the dispersed phase fluid by the continuous phase is very similar to that of droplet generation in a T-junction format-a protrusion of dispersed phase is sheared into droplets by the continuous phase. 27,28 The process we demonstrated here controls the displacement of the dispersed phase into the continuous phase and thus the droplet formation process.…”