Effects of viscosity on droplet formation and mixing in microfluidic channels

Tice, Joshua D.; Lyon, Adam D.; Ismagilov, Rustem F.

doi:10.1016/j.aca.2003.11.024

Cited by 326 publications

(274 citation statements)

References 23 publications

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“…Higher values of Ca > 0.1 result in laminar, continuous flow of immiscible fluids instead of discrete plug formation. 81 We have found that an equilibrium surface tension at the fluorous-aqueous interface of 10-20 mN m −1 is optimal for plug formation of aqueous protein and buffer solutions with viscosities close to that of water. All surfactants used in this study gave acceptable plug formation.…”

Section: Resultsmentioning

confidence: 96%

Controlling Nonspecific Protein Adsorption in a Plug-Based Microfluidic System by Controlling Interfacial Chemistry Using Fluorous-Phase Surfactants

2004

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Control of surface chemistry and protein adsorption is important for using microfluidic devices for biochemical analysis and high-throughput screening assays. This paper describes the control of protein adsorption at the liquid-liquid interface in a plug-based microfluidic system. The microfluidic system uses multiphase flows of immiscible fluorous and aqueous fluids to form plugs, which are aqueous droplets that are completely surrounded by fluorocarbon oil and do not come into direct contact with the hydrophobic surface of the microchannel. Protein adsorption at the aqueous-fluorous interface was controlled by using surfactants that were soluble in fluorocarbon oil but insoluble in aqueous solutions. Three perfluorinated alkane surfactants capped with different functional groups were used: a carboxylic acid, an alcohol, and a triethylene glycol group that was synthesized from commercially available materials. Using complementary methods of analysis, adsorption was characterized for several proteins (bovine serum albumin (BSA) and fibrinogen), including enzymes (ribonuclease A (RNase A) and alkaline phosphatase). These complementary methods involved characterizing adsorption in microliter-sized droplets by drop tensiometry and in nanoliter plugs by fluorescence microscopy and kinetic measurements of enzyme catalysis. The oligoethylene glycolcapped surfactant prevented protein adsorption in all cases. Adsorption of proteins to the carboxylic acid-capped surfactant in nanoliter plugs could be described by using the Langmuir model and tensiometry results for microliter drops. The microfluidic system was fabricated using rapid prototyping in poly(dimethylsiloxane) (PDMS). Black PDMS micro-fluidic devices, fabricated by curing a suspension of charcoal in PDMS, were used to measure the changes in fluorescence intensity more sensitively. This system will be useful for microfluidic bioassays, enzymatic kinetics, and protein crystallization, because it does not require surface modification during fabrication to control surface chemistry and protein adsorption. This paper describes the biocompatibility of a plug-based microfluidic system obtained through control of surface chemistry the aqueous-fluorous interface. This microfluidic system uses multiphase flows of immiscible fluorous and aqueous liquids to form droplets (plugs) and to transport them with rapid mixing and no Taylor-like dispersion. 1 We have previously used the system to measure enzyme kinetics 2 and perform protein crystallization 3-6 using submicroliter volumes of sample.

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Section: Resultsmentioning

confidence: 96%

Controlling Nonspecific Protein Adsorption in a Plug-Based Microfluidic System by Controlling Interfacial Chemistry Using Fluorous-Phase Surfactants

2004

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“…The ratio of flow rates (Q ¼ Q d =Q c ) and the viscosity ratio (k ¼ g d =g c ) are two important dimensionless numbers to characterize the droplet breakup, which has been confirmed by a wide range of experimental and numerical investigations. 18,19,23,25,26,37,57 The geometrical parameters, w c , w d , and h, lead to two additional dimensionless parameters characterizing the geometry. One is the ratio of the channel depth to the inlet width of the continuous phase (C ¼ h=w c ), and the other is the ratio of the inlet widths of the two phases (K ¼ w d =w c ).…”

Section: -3mentioning

confidence: 99%

Droplet formation in microfluidic cross-junctions

2011

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Using a lattice Boltzmann multiphase model, three-dimensional numerical simulations have been performed to understand droplet formation in microfluidic cross-junctions at low capillary numbers. Flow regimes, consequence of interaction between two immiscible fluids, are found to be dependent on the capillary number and flow rates of the continuous and dispersed phases. A regime map is created to describe the transition from droplets formation at a cross-junction (DCJ), downstream of cross-junction to stable parallel flows. The influence of flow rate ratio, capillary number, and channel geometry is then systematically studied in the squeezing-pressure-dominated DCJ regime. The plug length is found to exhibit a linear dependence on the flow rate ratio and obey power-law behavior on the capillary number. The channel geometry plays an important role in droplet breakup process. A scaling model is proposed to predict the plug length in the DCJ regime with the fitting constants depending on the geometrical parameters.

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“…1) made in glass polydimethylsiloxane (PDMS) by using soft lithography technology (Duffy et al 1998). When two immiscible fluids are injected, various flows such as droplets, pearl neacklaces, disordered patterns or parallel flows can be obtained after the junction (Squires and Quake 2005;Thorsen et al 2001;Tice et al 2004;Guillot and Colin 2005;Guillot et al 2007). However, in a wide range of flow rates, the two immiscible fluids flow side by side forming a laminar parallel flow.…”

Section: Principle Of the Microrheometermentioning

confidence: 99%

Towards a continuous microfluidic rheometer

Guillot

Moulin

Kötitz

et al. 2008

Microfluid Nanofluid

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In a previous paper we presented a way to measure the rheological properties of complex fluids on a microfluidic chip (Guillot et al., Langmuir 22:6438, 2006). The principle of our method is to use parallel flows between two immiscible fluids as a pressure sensor. In fact, in a such flow, both fluids flow side by side and the size occupied by each fluid stream depends only on both flow rates and on both viscosities. We use this property to measure the viscosity of one fluid knowing the viscosity of the other one, both flow rates and the relative size of both streams in a cross-section. We showed that using a less viscous fluid as a reference fluid allows to define a mean shear rate with a low standard deviation in the other fluid. This method allows us to measure the flow curve of a fluid with less than 250 lL of fluid. In this paper we implement this principle in a fully automated set up which controls the flow rate, analyzes the picture and calculates the mean shear rate and the viscosity of the studied fluid. We present results obtained for Newtonian fluids and complex fluids using this set up and we compare our data with cone and plate rheometer measurements. By adding a mixing stage in the fluidic network we show how this set up can be used to characterize in a continuous way the evolution of the rheological properties as a function of the formulation composition. We illustrate this by measuring the rheological curve of four formulations of polyethylene oxide solution with only 1.3 mL of concentrated polyethylene oxide solution. This method could be very useful in screening processes where the viscosity range and the behavior of the fluid to an applied stress must be evaluated.

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Effects of viscosity on droplet formation and mixing in microfluidic channels

Cited by 326 publications

References 23 publications

Controlling Nonspecific Protein Adsorption in a Plug-Based Microfluidic System by Controlling Interfacial Chemistry Using Fluorous-Phase Surfactants

Controlling Nonspecific Protein Adsorption in a Plug-Based Microfluidic System by Controlling Interfacial Chemistry Using Fluorous-Phase Surfactants

Droplet formation in microfluidic cross-junctions

Towards a continuous microfluidic rheometer

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