Density and viscosity ratio effects in droplet formation

Effects of Junction Angle and Viscosity Ratio on Droplet Formation in Microfluidic Cross-Junction

Journal of Fluids Engineering ◽

10.1115/1.4031881 ◽

2016 ◽

Vol 138 (5) ◽

Cited By ~ 13

Author(s):

Ich-Long Ngo ◽

Sang Woo Joo ◽

Chan Byon

Keyword(s):

Droplet Size ◽

Viscosity Ratio ◽

Nanoparticle Synthesis ◽

Droplet Formation ◽

Two Dimensional ◽

Flow Conditions ◽

Hydrogel Bead ◽

Water Fraction ◽

Side Channels ◽

Junction Angle

This study describes the dynamic behaviors of droplet formation in microfluidic cross-junction devices (MFCDs) based on a two-dimensional numerical model using the volume of fluid (VOF) method. The effects of the junction angle (ϕ = 30 to 90 deg) between the main and side channels and the viscosity ratios (β = 10−5 to 2.0) are considered. The numerical results indicate that the active area for droplet formation in the alternating digitized pattern formation (ADPF) generally increases with the decrease of ϕ at the same water fraction (wf). A junction angle of around 60 deg was predicted as the most efficient angle at which alternating droplets are still formed at lower capillary numbers (Ca). In addition, the droplet size in ADPF decreases as ϕ increases with the same flow conditions. When ϕ is less than 90 deg and prior to approaching the equilibrium state, there always exists a periodic deviation in the relative distance between droplets. The frequency of droplet generation in ADPF decreases as ϕ decreases, and it decreases more quickly when ϕ is less than 60 deg. In addition, the throughput of MFCDs can be controlled effectively as a function of ϕ, wf, and Ca. The droplet formation in MFCDs depends significantly on the viscosity ratio β, and the ADPF becomes a jetting formation (JF) when β is greater than unity. Furthermore, the droplet size in ADPF decreases with the increase of β. The understanding of droplet formation in MFCDs is very useful for many applications, such as nanoparticle synthesis with different concentrations, hydrogel bead generation, or cell transplantation in biomedical therapy.

Download Full-text

Parametric Study of Droplet Formation and Characteristics Within Microfluidic Devices — A Case Study

International Journal of Applied Mechanics ◽

10.1142/s1758825120500775 ◽

2020 ◽

Vol 12 (07) ◽

pp. 2050077

Author(s):

Seyedeh Sarah Salehi ◽

Amir Shamloo ◽

Siamak Kazemzadeh Hannani

Keyword(s):

Interfacial Tension ◽

Physical Properties ◽

Flow Rate ◽

Viscosity Ratio ◽

Droplet Formation ◽

Continuous Phase ◽

Phase Flow ◽

Phase Density ◽

Size And Shape ◽

The Impact

Droplet-based microfluidics technologies hold great attention in a wide range of applications, including chemical analysis, drug screening, and food industries. This work aimed to describe the effects of different physical properties of the two immiscible phases on droplet formation in a flow-focusing microfluidic device and determining proper flow rates to form a droplet within the desired size range. A numerical model was developed to solve the governing equations of two-phase flow and the results were validated with previous experimental results. The results demonstrate different types of droplet formation regimes from dripping to jetting and different production rates of droplets as a consequence of the impact of each property on fluid flow, including the viscosity ratio, density, interfacial tension, and the flow rate ratio. Based on the results, flow rate, viscosity, and interfacial tension strongly affect the droplet formation regime as well as its size and shape. Droplet diameter increases by increasing the dispersed to continuous phase flow rate as well as the interfacial tension while it decreases by increasing the viscosity ratio and the continuous phase density. Moreover, the formation of satellite droplets was modeled, and the effect of interfacial tension, the viscosity of the dispersed phase and the continuous phase density were found to be important on the conditions that the satellite droplets are suppressed. Since the formation of the satellite droplets induces polydispersity in droplet size, this phenomenon is avoided. Collectively, choosing appropriate aqueous and oil phases with proper physical properties is crucial in forming monodisperse droplets with defined size and shape.

Download Full-text

Lattice Boltzmann Simulation of Droplet Generation in a Microfluidic Cross-Junction

Communications in Computational Physics ◽

10.4208/cicp.231009.101110s ◽

2011 ◽

Vol 9 (5) ◽

pp. 1235-1256 ◽

Cited By ~ 19

Author(s):

Haihu Liu ◽

Yonghao Zhang

Keyword(s):

Droplet Size ◽

Flow Rate ◽

Lattice Boltzmann ◽

Capillary Number ◽

Rate Ratio ◽

Viscosity Ratio ◽

Droplet Formation ◽

Continuous Phase ◽

Viscous Force ◽

Flow Rate Ratio

AbstractUsing the lattice Boltzmann multiphase model, numerical simulations have been performed to understand the dynamics of droplet formation in a microfluidic cross-junction. The influence of capillary number, flow rate ratio, viscosity ratio, and viscosity of the continuous phase on droplet formation has been systematically studied over a wide range of capillary numbers. Two different regimes, namely the squeezinglike regime and the dripping regime, are clearly identified with the transition occurring at a critical capillary number Cacr. Generally, large flow rate ratio is expected to produce big droplets, while increasing capillary number will reduce droplet size. In the squeezing-like regime (Ca ≤ Cacr), droplet breakup process is dominated by the squeezing pressure and the viscous force; while in the dripping regime (Ca ≤ Cacr), the viscous force is dominant and the droplet size becomes independent of the flow rate ratio as the capillary number increases. In addition, the droplet size weakly depends on the viscosity ratio in both regimes and decreases when the viscosity of the continuous phase increases. Finally, a scaling law is established to predict the droplet size.

Download Full-text

Split or slip – passive generation of monodisperse double emulsions with cores of varying viscosity in microfluidic tandem step emulsification system

RSC Advances ◽

10.1039/d0ra03007d ◽

2020 ◽

Vol 10 (39) ◽

pp. 23058-23065

Author(s):

Adam S. Opalski ◽

Karol Makuch ◽

Ladislav Derzsi ◽

Piotr Garstecki

Keyword(s):

Viscosity Ratio ◽

Double Emulsion ◽

Droplet Formation ◽

Double Emulsions ◽

The Core ◽

System P ◽

Varying Viscosity

We investigate the role of fluid viscosities on formation of double emulsion in a microfluidic step emulsification system. The ratio of fluid viscosities controls double droplet formation, leading to splitting of the core for low core-to-shell viscosity ratio.

Download Full-text