Droplets and Bubbles in Microfluidic Devices

Anna, Shelley L.

doi:10.1146/annurev-fluid-122414-034425

Cited by 415 publications

(305 citation statements)

References 144 publications

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“…This mechanism likely explains the upper limit of viscosity ratio 0.1 for this process to happen. This value is comparable to the viscosity threshold for tip-streaming in hydrodynamic focusing [10].…”

Section: Images (B)-(d) Illustrate the Drop Modesmentioning

confidence: 64%

“…The droplets form an initially hexagonal pattern in the equatorial plane of the mother drop. The streaming occurs only for low viscosity drops, with viscosity ratio smaller than 0.1 and field strengths corresponding to Ca ∼ O (10).…”

Section: Images (B)-(d) Illustrate the Drop Modesmentioning

confidence: 99%

“…If the viscous stresses overcome the interfacial tension, the perturbation grows into a fluid filament. This is the tip-streaming phenomenon commonly observed in the microfluidic co-flow geometry [8][9][10]. If instead of a point, the flow is converging to a stagnation line, then a thin sheet can be entrained [11].…”

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confidence: 95%

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Streaming from the Equator of a Drop in an External Electric Field

Brosseau

Vlahovska

2017

Phys. Rev. Lett.

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Tip-streaming generates micron-and submicron-sized droplets when a thin thread pulled from the pointy end of a drop disintegrates. Here, we report streaming from the equator of a drop placed in a uniform electric field. The instability generates concentric fluid rings encircling the drop, which break up to form an array of microdroplets in the equatorial plane. We show that the streaming results from an interfacial instability at the stagnation line of the electrohydrodynamic flow, which creates a sharp rim. The flow draws from the rim a thin sheet which destabilizes and sheds fluid cylinders. This streaming phenomenon provides a new route for generating monodisperse microemulsions.A highly conducting drop in a uniform electric field elongates into a prolate ellipsoid whose poles in strong fields deform into conical tips (Taylor cones) emitting jets of charged tiny droplets [1][2][3][4][5]. This so called electrohydrodynamic (EHD) streaming or cone-jetting occurs in many natural phenomena (e.g., drops in thunderclouds) and technological applications (printing, electrospraying, electrospinning) [4,6].The streaming is related to a generic interfacial instability due to a convergent flow [7], see Figure 1.a. The interface is compressed and a local perturbation at the stagnation point (e.g., drop tips) gets drawn by the flow. If the viscous stresses overcome the interfacial tension, the perturbation grows into a fluid filament. This is the tip-streaming phenomenon commonly observed in the microfluidic co-flow geometry [8][9][10]. If instead of a point, the flow is converging to a stagnation line, then a thin sheet can be entrained [11]. By analogy with the cone-jet geometry resulting from the destabilization of a stagnation point, it is expected that the instability of a stagnation line would give rise to an edge-sheet structure. In this Letter, we report for the first time streaming resulting from a stagnation line instability.Experimentally, we exploit the electrohydrodynamic flow about a neutral drop placed in a uniform electric field [12,13]. By varying the fluid conductivities, we are able create flow converging either at the drop poles (Figure 1.b) to generate cone-jet, or at the equator ( Figure 1.c) to generate an edge-sheet. The latter case is the focus of this work. The electrohydrodynamic flow is driven by electric shear stresses due to induced surface charges [12,13]. For a drop in a uniform electric field the resulting flow is axisymmetrically aligned with the applied field. For a spherical drop with radius a placed in DC electric field E = Eẑ, the surface velocity is [12]where λ = µ in /µ ex is the viscosity ratio between the drop and suspending fluids and θ is the angle with the applied field direction. The direction of the surface flow depends on the difference of conductivity, σ, and permittivity, ε, of the drop and suspending fluids R = σ in /σ ex and S = ε in /ε ex . For highly conducting drops, R/S > 1, the surface flow is from the equator to the poles. Accordingly, the poles become stagnation p...

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Section: Images (B)-(d) Illustrate the Drop Modesmentioning

confidence: 64%

Section: Images (B)-(d) Illustrate the Drop Modesmentioning

confidence: 99%

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Streaming from the Equator of a Drop in an External Electric Field

Brosseau

Vlahovska

2017

Phys. Rev. Lett.

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“…When desorption energy is larger than coalescence, which is referred to as Pickering stabilisation . Adsorption of particles requires convective mass transfer (Anna 2016;BertonCarabin & Schroën 2015), and microfluidic devices that operate under convective mass transfer conditions are therefore expected to be useful for Pickering emulsion formation.…”

Section: Particles As Stabilisersmentioning

confidence: 99%

“…Transport towards the sub-surface is, therefore, assumed to be fast and adsorption is determined by diffusion through the subsurface and interface expansion rate. Diffusion through the sub-surface might be enhanced during Y-junction emulsification because the shear force from the continuous phase reduces the sub-surface thickness (Rayner et al 2005) and because of the curved interface (Anna 2016). To distinguish the two methods, the interfacial tension measured under dynamic mass transfer conditions is referred to as the acting interfacial tension (γ a ).…”

Section: Introductionmentioning

confidence: 99%

Microfluidic methods to study emulsion formation

Muijlwijk¹

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Advances in Microfluidics‐Based Technologies for Single Cell Culture

Alonso

et al. 2019

Adv. Biosys.

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Single cell culture has been considered one of the fundamental tools for single cell studies. Complex biological systems evolve from single cells, and the cells within biological systems are intrinsically heterogeneous. Therefore, culturing and understanding the behaviors of single cells are of great interest for both biological research and clinical studies. In recent years, advances in microfluidics‐based technologies have demonstrated unprecedented capabilities for single cell studies, and they have made high‐throughput single cell cultures possible. Microfluidic systems enable precise control of the microenvironment for single cell culture and monitoring of the behavior of single cells in real time. In addition, microfluidic devices can consist of upstream cell sorting and cell isolation, and they can also be seamlessly integrated with various downstream analysis methods. Therefore, microfluidic technologies can obtain data about the performance at the single‐cell level, providing information that cannot be achieved by studying the ensemble behavior of cell colonies. In this review, the recent developments in droplet‐based microfluidics, microwell‐based microfluidics, trap‐based microfluidics and SlipChip‐based microfluidics for the study of single cell culture is focused on. Perspectives on future improvement regarding single cell culture and its related research opportunities are also provided.

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Droplets and Bubbles in Microfluidic Devices

Cited by 415 publications

References 144 publications

Streaming from the Equator of a Drop in an External Electric Field

Streaming from the Equator of a Drop in an External Electric Field

Microfluidic methods to study emulsion formation

Advances in Microfluidics‐Based Technologies for Single Cell Culture

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