Breakup dynamics and dripping-to-jetting transition in a Newtonian/shear-thinning multiphase microsystem

Abstract

The breakup dynamics in non-Newtonian multiphase microsystems is associated with a variety of industrial applications such as food production and biomedical engineering. In this study, we numerically and experimentally characterize the dripping-to-jetting transition under various flow conditions in a Newtonian/shear-thinning multiphase microsystem. Our work can help to predict the formation of undesirable satellite droplets, which is one of the challenges in dispensing non-Newtonian fluids. We also demonstrate the variations in breakup dynamics between shear-thinning and Newtonian fluids under the same flow conditions. For shear-thinning fluids, the droplet size increases when the capillary number is smaller than a critical value, while it decreases when the capillary number is beyond the critical value. The variations highlight the importance of rheological effects in flows with a non-Newtonian fluid. The viscosity of shear-thinning fluids significantly affects the control over the droplet size, therefore necessitating the manipulation of the shear rate through adjusting the flow rate and the dimensions of the nozzle. Consequently, the droplet size can be tuned in a controlled manner. Our findings can guide the design of novel microdevices for generating droplets of shear-thinning fluids with a predetermined droplet size. This enhances the ability to fabricate functional particles using an emulsion-templated approach. Moreover, elastic effects are also investigated experimentally using a model shear-thinning fluid that also exhibits elastic behaviors: droplets are increasingly deformed with increasing elasticity of the continuous phase. The overall understanding in the model multiphase microsystem will facilitate the use of a droplet-based approach for non-Newtonian multiphase applications ranging from energy to biomedical sciences.

CFD study on Taylor bubble characteristics in Carreau‐Yasuda shear thinning liquids

“…The VOF method is most popular due its simplicity but at the same time it is precise enough that accounts for substantial curvature changes of the interface. [12,[36][37][38][39] It has also been proven that the VOF method accurately traced the interface with relatively lesser computational effort. [12] In our previous works, we also had implemented the VOF method for Taylor bubble formation in Newtonian and non-Newtonian systems.…”

Synthesis of Functional Materials by Non-Newtonian Microfluidic Multiphase System

“…Emulsion droplets can be passively formed by fluid instabilities using four of the most prevalent microfluidic geometries found from literature: coaxial [17], flow focusing [18], T junction [19], and step emulsification [20]. The dynamics of the droplet formation in microsystem can be characterized by a transition from dripping to jetting regime, governed by the Weber number of the dispersed phase, We in , defining the ratio of inertial force to surface tension and the capillary number of the continuous phase, Ca out , defining the ratio of viscous force to surface tension:…”

“…The dripping-to-jetting transition under various flow conditions in a Newtonian/shearthinning multiphase microsystem was characterized [17]. A numerical model of the microcapillary co-flow device has been developed with a Newtonian fluid injected in a cylindrical capillary as the dispersed phase at a constant average velocity V DP and a non-Newtonian outer phase injected through the coaxial square capillary as the continuous phase at a constant average velocity V CP (see Figure 2).…”

“…The flow patterns at different ratios of flow rate with viscoelastic continuous phase of 5% w/v PAA solution and dispersed phase of silicon oil were characterized [17]. The elastic forces from viscoelastic continuous phase help to overcome interfacial tension and thus facilitate transition to jetting at smaller magnitudes of the viscous forces.…”

Dynamics of double emulsion break-up in three phase glass capillary microfluidic devices

“…The VOF-CSF method has shown a good capability in predicting droplet formation in various microfluidic geometries [16,30,[35][36][37], but it has never been used to simulate droplet formation in three-liquid phase 3D microfluidic devices [15]. The results can be used to improve the current understanding of hydrodynamic flow focusing in multi-liquid phase microfluidic systems and discover the physics underlying pinch-off of double emulsion droplets in dripping, narrowing jetting and widening jetting regimes.…”