Pillar-induced droplet merging in microfluidic circuits

Niu, Xize; Gulati, Shelly; Edel, Joshua B.; deMello, Andrew J.

doi:10.1039/b813325e

Cited by 330 publications

(305 citation statements)

References 24 publications

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“…This means that the velocities observed during the merging process should decay rapidly and that the fluids should lose the memory of the violent event shortly after the merging. The fusion of two droplets containing separate reagents will therefore lead to a sharp interface between the chemical species, as seen for instance in the SI movies of Niu et al 94 where alternating whiteblack drops are merged. The reaction that occurs between the contents of the two drops can therefore proceed through a reaction-diffusion process 91 or after mixing of the species by the flow.…”

Section: B Active Fusion Approachesmentioning

confidence: 99%

Dynamics of microfluidic droplets

2010

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This critical review discusses the current understanding of the formation, transport, and merging of drops in microfluidics. We focus on the physical ingredients which determine the flow of drops in microchannels and recall classical results of fluid dynamics which help explain the observed behaviour. We begin by introducing the main physical ingredients that differentiate droplet microfluidics from single-phase microfluidics, namely the modifications to the flow and pressure fields that are introduced by the presence of interfacial tension. Then three practical aspects are studied in detail: (i) The formation of drops and the dominant interactions depending on the geometry in which they are formed.(ii) The transport of drops, namely the evaluation of drop velocity, the pressure-velocity relationships, and the flow field induced by the presence of the drop. (iii) The fusion of two drops, including different methods of bridging the liquid film between them which enables their merging.

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Section: B Active Fusion Approachesmentioning

confidence: 99%

Dynamics of microfluidic droplets

2010

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“…These two apparently contradictory requirements can either be applied separately, or they can be combined by placing discrete pillars for guiding droplets in a wide channel, as shown recently. 27 Furthermore, the value of the heating time can be manipulated by varying the volume of fluid that is heated, for example by reducing the channel thickness.…”

Section: Discussionmentioning

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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“…The utility of periodic control of droplets provides broad applicability in microfluidic biochemical reactions which require time and volume-dependent reactions. Furthermore, other microfluidic components such as pillar microstructure 21 and built-in electrode 22 can be applied to enhanced coalescence of droplets for achieving advanced combinatorial reactions in a large scale screening applications. Particularly, current platform can be adapted to carry out on-chip serial dilution for measuring rapid enzymatic kinetics, studying protein-protein interactions and performing biological dilution assays.…”

Section: Resultsmentioning

confidence: 99%

Microbridge structures for uniform interval control of flowing droplets in microfluidic networks

Lee

et al. 2011

Biomicrofluidics

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Precise temporal control of microfluidic droplets such as synchronization and combinatorial pairing of droplets is required to achieve a variety range of chemical and biochemical reactions inside microfluidic networks. Here, we present a facile and robust microfluidic platform enabling uniform interval control of flowing droplets for the precise temporal synchronization and pairing of picoliter droplets with a reagent. By incorporating microbridge structures interconnecting the dropletcarrying channel and the flow control channel, a fluidic pressure drop was derived between the two fluidic channels via the microbridge structures, reordering flowing droplets with a defined uniform interval. Through the adjustment of the control oil flow rate, the droplet intervals were flexibly and precisely adjustable. With this mechanism of droplet spacing, the gelation of the alginate droplets as well as control of the droplet interval was simultaneously achieved by additional control oil flow including calcified oleic acid. In addition, by parallel linking identical microfluidic modules with distinct sample inlet, controlled synchronization and pairing of two distinct droplets were demonstrated. This method is applicable to facilitate and develop many droplet-based microfluidic applications, including biological assay, combinatorial synthesis, and high-throughput screening.

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Pillar-induced droplet merging in microfluidic circuits

Cited by 330 publications

References 24 publications

Dynamics of microfluidic droplets

Dynamics of microfluidic droplets

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

Microbridge structures for uniform interval control of flowing droplets in microfluidic networks

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