A new device for the generation of microbubbles

Gordillo, José Manuel; Cheng, Zhengdong; Gañán‐Calvo, Alfonso M.; Márquez, Manuel; Weitz, David A.

doi:10.1063/1.1737739

Cited by 104 publications

(83 citation statements)

References 11 publications

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“…Several techniques exist for formation of droplets [1][2][3][4][5][6][7][8][9][10][11][12] and bubbles. [13][14][15][16][17][18] These systems enable formation of dispersions with highly attractive features, particularly the control over the size and volume fraction of the dispersed phase, 3,6,14,15,32 and narrow distribution of the sizes of individual droplets or bubbles. 3,10,14,15 Microfluidic dispersion-generators can also produce, in a highly controllable fashion, solid particles [37][38][39][40][41] and arrays of liquid crystalline droplets.…”

Section: Bubbles and Drops In Microfluidicsmentioning

confidence: 99%

Formation of droplets and bubbles in a microfluidic T-junction—scaling and mechanism of break-up

et al. 2006

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This article describes the process of formation of droplets and bubbles in microfluidic T-junction geometries. At low capillary numbers break-up is not dominated by shear stresses: experimental results support the assertion that the dominant contribution to the dynamics of break-up arises from the pressure drop across the emerging droplet or bubble. This pressure drop results from the high resistance to flow of the continuous (carrier) fluid in the thin films that separate the droplet from the walls of the microchannel when the droplet fills almost the entire cross-section of the channel. A simple scaling relation, based on this assertion, predicts the size of droplets and bubbles produced in the T-junctions over a range of rates of flow of the two immiscible phases, the viscosity of the continuous phase, the interfacial tension, and the geometrical dimensions of the device.

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Section: Bubbles and Drops In Microfluidicsmentioning

confidence: 99%

Formation of droplets and bubbles in a microfluidic T-junction—scaling and mechanism of break-up

et al. 2006

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“…The flow focusing device is based on continuously focusing gas and liquid through a small orifice ($ 400 mm), thereby creating a jet of gas which becomes unstable and breaks up into monodisperse bubbles. 15,16,17,18 The production is up to 200 bubbles s À1 and we can achieve diameters within the range of 100-700 mm, using different ratios of flow rates of gas and liquid. For the creation of monolayers or the crystalline bubble structures consisting of up to 23 layers on top of a liquid surface we only used the flow focusing device, i.e.…”

Section: Experiments and Analysismentioning

confidence: 99%

Rearrangement and elimination of ordered surface layers of crystalline bubble structures due to gas diffusion

2009

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We describe a hitherto unknown self-organising effect in wet crystalline bubble structures exposed to air. Due to the escape of gas from the bubbles in the top surface layer, bubbles shrink and create space for the bubbles of the lower layers to interpose themselves at the top. This occurs irregularly, but finally a newly ordered bidisperse top layer is formed. This process can be followed for several episodes of elimination of surface layers. The crystalline orientation influences the speed of shrinkage and formation of the bidisperse top layer. Compared with diffusion of a single bubble or monodisperse monolayer on top of a liquid pool, the diffusion is much faster. This may be accounted for by the extra buoyancy force leading to a larger exposure of the bubbles at the surface.

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“…28 An example can be found in the large number of micro devices based on the so-called flow-focusing configuration, where an inner gas stream, surrounded by an outer liquid co-flow, is driven through a small orifice. [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.…”

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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A new device for the generation of microbubbles

Cited by 104 publications

References 11 publications

Formation of droplets and bubbles in a microfluidic T-junction—scaling and mechanism of break-up

Formation of droplets and bubbles in a microfluidic T-junction—scaling and mechanism of break-up

Rearrangement and elimination of ordered surface layers of crystalline bubble structures due to gas diffusion

Bubbling in a co-flow at high Reynolds numbers

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