Bubble dispenser in microfluidic devices

Cubaud, Thomas; Tatineni, Mahidhar; Zhong, Xiaolin; Ho, Chih‐Ming

doi:10.1103/physreve.72.037302

Cited by 132 publications

(101 citation statements)

References 24 publications

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“…This mechanism was first proposed by Garstecki et al (2006), where the functional form V (Q) was observed experimentally. Cubaud et al (2005) observed a similar behaviour for bubble formation in a symmetric cross-junction. We verified this result for the drop volume with our numerical simulations.…”

Section: Resultssupporting

confidence: 62%

Transition from squeezing to dripping in a microfluidic T-shaped junction

et al. 2008

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We describe the results of a numerical investigation of the dynamics of breakup of streams of immiscible fluids in the confined geometry of a microfluidic T-junction. We identify three distinct regimes of formation of droplets: squeezing, dripping and jetting, providing a unifying picture of emulsification processes typical for microfluidic systems. The squeezing mechanism of breakup is particular to microfluidic systems, since the physical confinement of the fluids has pronounced effects on the interfacial dynamics. In this regime, the breakup process is driven chiefly by the buildup of pressure upstream of an emerging droplet and both the dynamics of breakup and the scaling of the sizes of droplets are influenced only very weakly by the value of the capillary number. The dripping regime, while apparently homologous to the unbounded case, is also significantly influenced by the constrained geometry; these effects modify the scaling law for the size of the droplets derived from the balance of interfacial and viscous stresses. Finally, the jetting regime sets in only at very high flow rates, or with low interfacial tension, i.e. higher values of the capillary number, similar to the unbounded case.

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Section: Resultssupporting

confidence: 62%

Transition from squeezing to dripping in a microfluidic T-shaped junction

et al. 2008

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“…[29][30][31][32][33][34] In this particular configuration, dimensional analysis and physical arguments have provided with closed expressions for the scaling of the bubble size based on the different control parameters. 29,[32][33][34][35][36] However, although the proposed scaling laws are valid for practical purposes because they predict the bubble volume relatively well, a more detailed theoretical and numerical approach would be desirable to fully comprehend the bubble formation mechanisms. Making use of numerical simulations in the zero Reynolds number limit ͑Stokes flow͒, Jensen et al 37 have recently derived scaling laws to predict the volume of bubbles formed using the flow-focusing geometry that agree with previous experimental results.…”

Section: Introductionmentioning

confidence: 99%

Bubbling in a co-flow at high Reynolds numbers

2007

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The physical mechanisms underlying bubble formation from a needle in a co-flowing liquid environment at high Reynolds numbers are studied in detail with the aid of experiments and boundary-integral numerical simulations. To determine the effect of gas inertia the experiments were carried out with air and helium. The influence of the injection system is elucidated by performing experiments using two different facilities, one where the constancy of the gas flow-rate entering the bubble is ensured, and another one where the gas is injected through a needle directly connected to a pressurized chamber. In the case of constant flow-rate injection conditions, the bubbling frequency has been shown to hardly depend on the gas density, with a bubble size given by d b / r o Ӎ͓6U͑k * U + k 2 ͒ / ͑U −1͔͒ 1/3 for U տ 2, where U is the gas-to-liquid ratio of the mean velocities, r o is the radius of the gas injection needle, and k * = 5.84 and k 2 = 4.29, with d b / r o ϳ 3.3U 1/3 for U ӷ 1. Nevertheless, in this case the effect of gas density is relevant to describe the final instants of bubble breakup, which take place at a time scale much smaller than the bubbling time, t b . This effect is evidenced by the liquid jets penetrating the gas bubbles upon their pinch-off. Our measurements indicate that the velocity of the penetrating jets is considerably larger in air bubbles than in helium bubbles due to the distinct gas inertia of both situations. However, in the case of constant pressure supply conditions, the bubble size strongly depends on the density of the gas through the pressure loss along the gas injection needle. Furthermore, under the operating conditions reported here, the equivalent diameters of the bubbles are between 10% and 20% larger than their constant flow-rate counterparts. In addition, the experiments and the numerical results show that, under constant pressure supply, helium bubbles are approximately 10% larger than air bubbles due to the gas density effect on the bubbling process.

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“…Microfluidics appears to offer a promising new route to fabrication of these materials, enabling the production of highly uniform droplets, bubbles, and particles in the 10-100 micrometer size range. By flowing two or more immiscible liquids into a microfluidic device, numerous authors have demonstrated the ability to make emulsion droplets, 1-3 gas bubbles, 4,5 solid polymeric particles, [6][7][8] and even more novel particles including double emulsions, 9 polymeric particles with arbitrary nonspherical shapes, 10 spherical colloidal shells, 11 and Janus particles. 10 The highly ordered packing of the monodisperse droplets has also been used to template porous materials.…”

Section: Introduction and Background On Tipstreamingmentioning

confidence: 99%

Microscale tipstreaming in a microfluidic flow focusing device

2006

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A microfluidic flow-focusing device is used to explore the use of surfactant-mediated tipstreaming to synthesize micrometer-scale and smaller droplets. By controlling the surfactant bulk concentration of a soluble nonionic surfactant in the neighborhood of the critical micelle concentration, along with the capillary number and the ratio of the internal and external flow rates, we observe several distinct modes of droplet breakup. For the most part, droplet breakup in microfluidic devices results in highly monodisperse droplets in the range of tens of micrometers in size. However, we observe a new mode of breakup called "thread formation" that resembles tipstreaming and yields tiny droplets in the range of a few micrometers in size or smaller. In this work, we characterize the growth of the thread and its maximum length as a function of flow variables and surfactant content, and we also characterize the period of droplet breakup as a function of these variables. Our results suggest possible methods for controlling the process. Using a simple flow visualization experiment as the basis, we report on preliminary efforts to model the thread formation process.

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Bubble dispenser in microfluidic devices

Cited by 132 publications

References 24 publications

Transition from squeezing to dripping in a microfluidic T-shaped junction

Transition from squeezing to dripping in a microfluidic T-shaped junction

Bubbling in a co-flow at high Reynolds numbers

Microscale tipstreaming in a microfluidic flow focusing device

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