Water Droplets Translocation and Fission in a 3D Bi-Planar Multifurcated T-Junction Microchannels

Droplet fission has gained notable interest in drug delivery applications due to its ability to perform parallel operations in single device. Hitherto, droplet flow behavior in a 3D constriction was scarcely investigated. This study aims to investigate droplets fission inside a 3D bi-planar multifurcated microfluidic device. The flow behavior and droplet size distribution were studied in trifurcated microchannels using distilled water as dispersed phase (1 mPa·s) and olive oil (68 mPa·s) as continuous phase. Various sizes of subordinate daughter droplets were manipulated passively through the modulation of flowrate ratio (Q) (0.15 < Q < 3.33). Overall, we found droplet size coefficient of variations (CV%) ranging from 0.72% to 69%. Highly monodispersed droplets were formed at the upstream T-junction (CV% < 2%) while the droplet fission process was unstable at higher flowrate ratio (Q > 0.4) as they travel downstream (1.5% < CV% < 69%) to splitting junctions. Complex responses to the non-monotonic behavior of mean droplet size was found at the downstream boundaries, which arose from the deformations under nonuniform flow condition. CFD was used as a tool to study the preliminary maximum velocity (Umax) profile for the symmetrical (0.01334 m/s < Umax < 0.0153 m/s) and asymmetrical branched channels (0.0223 m/s< Umax < 0.00438 m/s), thus complementing the experimental model studies.

Droplet Formation and Fission in Shear-Thinning/Newtonian Multiphase System Using Bilayer Bifurcating Microchannel

With a novel platform of bilayer polydimethylsiloxane microchannel formed by bifurcating junction, we aim to investigate droplet formation and fission in a multiphase system with complex three-dimensional (3D) structure and understand the variations in mechanism associated with droplet formation and fission in the microstructure between shear-thinning/Newtonian system versus Newtonian/Newtonian system. The investigation concentrates on shear-thinning fluid because it is one of the most ubiquitous rheological properties of non-Newtonian fluids. Sodium carboxymethyl cellulose (CMC) solution and silicone oil have been used as model fluids and numerical model has been established to characterize the shear-thinning effect in formation of CMC-in-oil emulsions, as well as breakup dynamics when droplets flow through 3D bifurcating junction. The droplet volume and generation rate have been compared between two systems at the same Weber number and capillary number. Variation in droplet fission has been found between two systems, demonstrating that the shear-thinning property and confining geometric boundaries significantly affect the deformation and breakup of each mother droplet into two daughter droplets at bifurcating junction. The understanding of the droplet fission in the novel microstructure will enable more versatile control over the emulsion formation and fission when non-Newtonian fluids are involved. The model systems in the study can be further developed to investigate the mechanical property of emulsion templated particles such as drug encapsulated microcapsules when they flow through complex media structures, such as blood capillaries or the porous tissue structure, which feature with bifurcating junction.

Droplet Fission in Non-Newtonian Multiphase System Using Bilayer Bifurcated Microchannel

In this paper, we present a novel design of bilayer polydimethylsiloxane (PDMS) microchannel formed by bifurcated junction, from which each curved branch lies on the upper and lower layer, respectively. With this 3D platform, we aim to investigate droplet formation and subsequent fission in a multiphase system using non-Newtonian fluids, which are ubiquitous in daily life and have been widely used in industrial applications including biomedical engineering, food production, personal care and cosmetics, and material synthesis. Numerical model has been established to characterize the non-Newtonian effect to droplet fission and associated breakup dynamics when droplet flows through 3D bifurcated junction, where droplets can deform significantly on account of the confining geometric boundaries, and the flow of the surrounding non-Newtonian liquid, both of which control the deformation and breakup of each mother droplet into two daughter droplets. Dispersions of sodium carboxymethyl cellulose in water, and dispersions of polyvinylchloride in dioctylphthalate have been used as model fluids in the study, with the former one possessing shear-thinning behaviour, while the latter one possessing shear-thickening behaviour. The understanding of the droplet fission in the novel microstructure will enable more versatile control over the emulsion formation when non-Newtonian fluids are involved. The model systems in the study can be further developed to investigate the mechanical property of emulsion templated particles such as drug encapsulated microcapsules when they flow through complex media structures, such as blood capillaries or the porous tissue structure, which feature with bifurcated junction.

Controllable geometry-mediated droplet fission using “off-the-shelf” capillary microfluidics device

We describe a cheap, easily assembled, controllable droplet fission device to obtain a variety of uniform daughter droplets.