Microfluidic bypass for efficient passive regulation of droplet traffic at a junction

Cristobal, Galder; Benoit, J.; Joanicot, Mathieu; Ajdari, Armand

doi:10.1063/1.2221929

Cited by 97 publications

(83 citation statements)

References 8 publications

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“…Since the cross-sectional geometries of the two branches are identical, we can assume that a, b, and c are the same for both branches. We can then rewrite eqn (14) to equate the pressure drops along the two branches. …”

Section: The Experimental Designmentioning

confidence: 99%

“…To design microfluidic networks that do not require valves or switches to route bubbles from one region of a device to the next, one must be able to predict the paths of the bubbles through the network. 14 Understanding how the pressure drop along a channel depends on the number and lengths of the bubbles that move through it is crucial to making these kinds of predictions.…”

Section: Introductionmentioning

confidence: 99%

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The pressure drop along rectangular microchannels containing bubbles

et al. 2007

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This paper derives the difference in pressure between the beginning and the end of a rectangular microchannel through which a flowing liquid (water, with or without surfactant, and mixtures of water and glycerol) carries bubbles that contact all four walls of the channel. It uses an indirect method to derive the pressure in the channel. The pressure drop depends predominantly on the number of bubbles in the channel at both low and high concentrations of surfactant. At intermediate concentrations of surfactant, if the channel contains bubbles (of the same or different lengths), the total, aggregated length of the bubbles in the channel is the dominant contributor to the pressure drop. The difference between these two cases stems from increased flow of liquid through the ''gutters''-the regions of the system bounded by the curved body of the bubble and the corners of the channel-in the presence of intermediate concentrations of surfactant. This paper presents a systematic and quantitative investigation of the influence of surfactants on the flow of fluids in microchannels containing bubbles. It derives the contributions to the overall pressure drop from three regions of the channel: (i) the slugs of liquid between the bubbles (and separated from the bubbles), in which liquid flows as though no bubbles were present; (ii) the gutters along the corners of the microchannels; and (iii) the curved caps at the ends of the bubble.

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Section: The Experimental Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The pressure drop along rectangular microchannels containing bubbles

et al. 2007

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“…These structures act as filters, allowing the oil to flow through them while forcing the drops to continue in the test channel 26 . The hydrodynamic resistance of the bypass is measured by flowing an aqueous suspension of tracer particles into the device and measuring the relative flow rates in the bypass and the test section, keeping in mind that the pressure gradient acting on the test section is the same as for the bypass.…”

Section: Experimental Microchannels and Microfluidicsmentioning

confidence: 99%

Laser-Induced Force on a Microfluidic Drop: Origin and Magnitude

Verneuil

Cordero

Gallaire³

et al. 2009

Langmuir

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The localized heating produced by a tightly focused infrared laser leads to surface tension gradients at the interface of microfluidic drops covered with surfactants, resulting in a net force on the drop whose origin and magnitude are the focus of this paper. First, by colocalization of the surfactant micelles with a fluorescent dye, we demonstrate that the heating alters their spatial distribution, driving the interface out of equilibrium. This soluto-capillary effect opposes and overcomes the purely thermal dependence of the surface tension, leading to reversed interfacial flows. As the surface of the drop is set into motion, recirculation rolls are created outside and inside the drop that we measure using time-resolved micro-Particle Image Velocimetry. Second, the net force produced on the drop is measured using an original microfluidic design. For a drop 300 µm-long and 100 µm wide we obtain a force of 180 † Laboratoire d'Hydrodynamique (LadHyX), Ecole Polytechnique, 91128 Palaiseau, France ‡ Laboratoire J.A. Dieudonné, Université de Nice Sophia-Antipolis, 06108 Nice, France § Current address:Department of Physics, University of Pennsylvania, Philadelphia, PA 1 Emilie Verneuil et al.Laser-induced force on a drop nN for a laser power of 100 mW. This micro-dynanometer further shows that the magnitude of the heating, which is determined by the laser power and its absorption in the water, sets the magnitude of the net force on the drop. On the other hand, the dynamics of the force generation is limited by the time scale for heating which has independently been measured to be τ Θ = 4 ms. This time scale sets the maximum velocity that the drops can have and still be blocked, by requiring that the interface passes the laser spot in a time longer than τ Θ . The maximum velocity is measured at U max = 0.7 mm/s for our geometric conditions. Finally, a scaling model is derived that describes the blocking force in a confined geometry as the result of the viscous stresses produced by the shear between the drop and the lateral walls.

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“…Motivated by this necessity, a field of research emerged that explores and develops methods to reproducibly generate (Garstecki et al 2006;Guillot and Colin 2005;Henkel et al 2004;Malsch et al 2008a, b;Nisisako et al 2002;Song et al 2003;Thorsen et al 2001;Zheng et al 2004), fuse Kielpinski et al 2006;Tan et al 2004) and split droplets Link et al 2004;Pollack et al 2002), dose liquid into droplets (Henkel et al 2004), sort and direct them (Cristobal et al 2006;Engl et al 2005;Schindler and Ajdari 2008) and perform phase separation (Kralj et al 2007;Voigt et al 2007). In addition, ''logic'' operations were developed (Prakash and Gershenfeld 2007), which have been successfully applied in smart operation units that implement fluidic closed-loop self-control for autonomous operation .…”

Section: Introductionmentioning

confidence: 99%

Dynamics of droplet formation at T-shaped nozzles with elastic feed lines

Malsch

Gleichmann

Kielpinski

et al. 2009

Microfluid Nanofluid

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We describe the formation of water in oil droplets, which are commonly used in lab-on-a-chip systems for sample generation and dosing, at microfluidic Tshaped nozzles from elastic feed lines. A narrow nozzle forms a barrier for a liquid-liquid interface, such that pressure can build up behind the nozzle up to a critical pressure. Above this critical pressure, the liquid bursts into the main channel. Build-up of pressure is possible when the fluid before the nozzle is compressible or when the channel that leads to the nozzle is elastic. We explore the value of the critical pressure and the time required to achieve it. We describe the fluid flow of the sudden burst, globally in terms of flow rate into the channel and spatially resolved in terms of flow fields measured using micro-PIV. A total of three different stages-the lag phase, a spill out phase, and a linear growth phase-can be clearly discriminated during droplet formation. The lag time linearly scales with the curvature of the interface inside the nozzle and is inversly proportional to the flow rate of the dispersed phase. A complete overview of the evolution of the growth of droplets and the internal flow structure is provided in the digital supplement.

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Microfluidic bypass for efficient passive regulation of droplet traffic at a junction

Cited by 97 publications

References 8 publications

The pressure drop along rectangular microchannels containing bubbles

The pressure drop along rectangular microchannels containing bubbles

Laser-Induced Force on a Microfluidic Drop: Origin and Magnitude

Dynamics of droplet formation at T-shaped nozzles with elastic feed lines

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