Formation of dispersions using “flow focusing” in microchannels

Anna, Shelley L.; Bontoux, Nathalie; Stone, Howard A.

doi:10.1063/1.1537519

Cited by 2,017 publications

(1,747 citation statements)

References 15 publications

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“…21,22 Several methods of forming droplets in microfluidic channels have been described, and gas bubbles have also been used to enhance the mixing of liquids. 1,[23][24][25][26] To perform multi-step, time controlled syntheses with this droplet-based microfluidic method, additional reagent must be added to the droplets formed from initial reagents. Previously, we accomplished this addition by merging one stream of droplets with a second stream of droplets.…”

Section: Introductionmentioning

confidence: 99%

Multi-step synthesis of nanoparticles performed on millisecond time scale in a microfluidic droplet-based system

2004

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This paper reports a plug-based, microfluidic method for performing multi-step chemical reactions with millisecond time-control. It builds upon a previously reported method where aqueous reagents were injected into a flow of immiscible fluid (fluorocarbons) (H. Song et al., Angew. Chem. Int. Ed., 2003, 42, 768). The aqueous reagents formed plugs -droplets surrounded and transported by the immiscible fluid. Winding channels rapidly mixed the reagents in droplets. This paper shows that further stages of the reaction could be initiated by flowing additional reagent streams directly into the droplets of initial reaction mixture. The conditions necessary for an aqueous stream to merge with aqueous droplets were characterized. The Capillary number could be used to predict the behavior of the two-phase flow at the merging junction. By transporting solid reaction products in droplets, the products were kept from aggregating on the walls of the microchannels. To demonstrate the utility of this microfluidic method it was used to synthesize colloidal CdS and CdS/CdSe core-shell nanoparticles.

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Section: Introductionmentioning

confidence: 99%

Multi-step synthesis of nanoparticles performed on millisecond time scale in a microfluidic droplet-based system

2004

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“…Indeed, a drop may be formed with a known composition and volume [5,6,7] and transported by an inert fluid without loss of the solute species and without cross-contamination [8]. Furthermore, fusion of two drops containing two reactive species leads to the onset, on demand, of a reaction [9] whose product may be sampled by breaking the drop at a bifurcation [10].…”

Section: Introductionmentioning

confidence: 99%

An optical toolbox for total control of droplet microfluidics

2007

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The use of microfluidic drops as microreactors hinges on the active control of certain fundamental operations, such as droplet formation, transport, division and fusion. Recent work has demonstrated that local heating from a focused laser can apply a thermocapillary force on a liquid interface sufficient to block the advance of a droplet in a microchannel (Baroud et al., Phys. Rev. E. V 75, p.046302). Here, we demonstrate the usefulness of this optical approach by implementing the operations mentioned above, without the need for any special microfabrication or moving parts. Building blocks such as a droplet valve, sorter, fuser, or divider are shown, as is the combination of a valve and fuser using a single laser spot.

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“…4B). [18][19][20] Immiscible fluids can be difficult to handle under pressure-driven flow because the applied pressure should be higher than capillary pressure but not so high to generate an excessive capillary number that would cause droplet deformation. 21 Also, when multiple inlets are controlled with different pressures, liquid could potentially flow from one cup to another.…”

Section: Generation Of Flow For Solutions Of Different Viscositiesmentioning

confidence: 99%

The pumping lid: investigating multi-material 3D printing for equipment-free, programmable generation of positive and negative pressures for microfluidic applications

et al. 2014

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Equipment-free pumping is a challenging problem and an active area of research in microfluidics, with applications for both laboratory and limited-resource settings. This paper describes the pumping lid method, a strategy to achieve equipment-free pumping by controlled generation of pressure. Pressure was generated using portable, lightweight, and disposable parts that can be integrated with existing microfluidic devices to simplify workflow and eliminate the need for pumping equipment. The development of this method was enabled by multi-material 3D printing, which allows fast prototyping, including composite parts that combine materials with different mechanical properties (e.g. both rigid and elastic materials in the same part). The first type of pumping lid we describe was used to produce predictable positive or negative pressures via controlled compression or expansion of gases. A model was developed to describe the pressures and flow rates generated with this approach and it was validated experimentally. Pressures were pre-programmed by the geometry of the parts and could be tuned further even while the experiment was in progress. Using multiple lids or a composite lid with different inlets enabled several solutions to be pumped independently in a single device. The second type of pumping lid, which relied on vapor-liquid equilibrium to generate pressure, was designed, modeled, and experimentally characterized. The pumping lid method was validated by controlling flow in different types of microfluidic applications, including the production of droplets, control of laminar flow profiles, and loading of SlipChip devices. We believe that applying the pumping lid methodology to existing microfluidic devices will enhance their use as portable diagnostic tools in limited resource settings as well as accelerate adoption of microfluidics in laboratories.

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Formation of dispersions using “flow focusing” in microchannels

Cited by 2,017 publications

References 15 publications

Multi-step synthesis of nanoparticles performed on millisecond time scale in a microfluidic droplet-based system

Multi-step synthesis of nanoparticles performed on millisecond time scale in a microfluidic droplet-based system

An optical toolbox for total control of droplet microfluidics

The pumping lid: investigating multi-material 3D printing for equipment-free, programmable generation of positive and negative pressures for microfluidic applications

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