Reaction-diffusion dynamics: Confrontation between theory and experiment in a microfluidic reactor

Baroud, Charles N.; Okkels, Fridolin; Ménétrier, Laure; Tabeling, Patrick

doi:10.1103/physreve.67.060104

Cited by 87 publications

(81 citation statements)

References 9 publications

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“…Several experimental works in gels have validated these RD scalings using A þ B-C types of reaction, see Koo et al (1990), Taitelbaum et al (1992) and Yen et al (1996), like for instance the complexation reaction of Cu 2 þ with a substrate studied by Koo and Kopelman (1991) in an agarose gel. More recently, a different type of convection-free experiment carried out by Baroud et al (2003) in a T-shaped microfluidic reactor has further confirmed these RD scalings using the binding reaction of Ca 2 þ with calcium green. All these experiments are not only in excellent agreement with the theoretical scalings, but the actual positions of the reaction front are very close to the predicted theoretical values.…”

Section: Introductionmentioning

confidence: 58%

“…The various chemical reactions that have been used to verify the RD scalings predicted by G alfi and Racz (1988) could be used to compare with our theoretical results. These reactions have kinetic constants ranging between k $ 10 À1 and $ 10 6 M À1 s À1 , see Baroud et al (2003), Koo and Kopelman (1991) and Taitelbaum et al (1992), which, along with the initial reactant concentration a 0 between 5:0 Â 10 À5 M and 1:0 Â 10 À3 M, gives characteristic times t c ¼ 1=ðka o Þ varying between t c ¼ 10 À3 s and t c ¼ 2 Â 10 5 . The diffusion coefficients of the involved species are equal to D $ 3:028:0 Â 10 À6 cm 2 =s, see Baroud et al (2003), Koo and Kopelman (1991) and Taitelbaum et al (1992), corresponding to characteristic length scales L c ¼ ffiffiffiffiffiffiffiffi Dt c p running between 5:5 Â 10 À4 mm and 1:2 cm.…”

Section: Experimental Values Of Physical Parametersmentioning

confidence: 99%

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Influence of buoyancy-driven convection on the dynamics of A+B→C reaction fronts in horizontal solution layers

Rongy

Trevelyan

Wit

2010

Chemical Engineering Science

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a b s t r a c tThe dynamics of initially vertical A þ B-C reaction fronts propagating in covered horizontal solution layers can be influenced by buoyancy-driven convection. Experiments have provided evidence that a much faster propagation of the front occurs in solutions than that predicted by reaction-diffusion (RD) theories, thereby suggesting the influence of convective effects arising if A, B, and C have different densities. Here we analyze numerically and theoretically the dynamics resulting from the coupling of a simple A þ B-C chemical reaction with diffusion and convection induced by density differences across the reaction front. The important parameters of the related reaction-diffusion-convection (RDC) model are the three dimensionless Rayleigh numbers, quantifying the contribution of each species concentration to the density of the solution, the layer thickness, and the initial reactant concentration ratio. The presence of buoyancy-driven convection at the front induces a propagation of this front even in the case of equal diffusion coefficients and equal initial reactant concentrations for which RD theories predict a non-moving front. In the case of equal initial concentrations, even in the presence of convection, the classification of the various possible dynamics and the prediction of the direction of front propagation can be obtained from simple criteria on the Rayleigh numbers. In the case of different initial reactant concentrations for which, in the absence of convection, the RD front propagates towards the side of the less concentrated reactant, the introduction of buoyancy convection not only invalidates the long time RD scalings but can lead to a double reversal in the direction of propagation of the reaction front for intermediate times. The influence of the different parameters on the RDC dynamics is presented.

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Section: Introductionmentioning

confidence: 58%

Section: Experimental Values Of Physical Parametersmentioning

confidence: 99%

Influence of buoyancy-driven convection on the dynamics of A+B→C reaction fronts in horizontal solution layers

Rongy

Trevelyan

Wit

2010

Chemical Engineering Science

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“…how the reaction product, C, turns into precipitate). While the front properties have been thoroughly studied and understood both theoretically [17,18] and experimentally [19,20], the dynamics of precipitation is more debated [13,18]. The competing pre-and post-nucleation views can be combined [18,21], and we shall use a simple version [14] based on the Cahn-Hilliard equation with noise added [22][23][24].…”

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confidence: 99%

Probability of the Emergence of Helical Precipitation Patterns in the Wake of Reaction-Diffusion Fronts

et al. 2013

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Helical and helicoidal precipitation patterns emerging in the wake of reaction-diffusion fronts are studied. In our experiments, these chiral structures arise with well defined probabilities PH controlled by conditions such as e.g., the initial concentration of the reagents. We develop a model which describes the observed experimental trends. The results suggest that PH is determined by a delicate interplay among the time-and length-scales related to the front and to the unstable precipitation modes and, furthermore, the noise amplitude also plays a quantifiable role.PACS numbers: 68.35.Ct Helices and helicoids are present from nano-to macroscale (ZnO nanohelices [1], macromolecules and inorganic crystals with a helical structure [2, 3], precipitation helices [4][5][6], fiber geometry of heart walls [7]). Formation of these fascinating structures generally follows two routes. First, templates with chiral symmetry (e.g., oragogel fibers) may exist in the system, and the symmetry is just transcribed to a structure (e.g., inorganic materials [8]) at a larger scale. Second, spontaneous symmetry breaking may occur through the self-assembly of achiral building blocks into a helical/helicoidal structure, as e.g. in case of crystals with chiral morphology [2,9].Theoretically, the symmetry-breaking route is more interesting. Universal aspects may emerge and the robust features of this self-organization process may be important for applications as well. Indeed, control over creating helical structures would make engineering (in particular, the bottom-up design of micro-patterns [10]) more flexible since chiral morphology of materials are known to affect their physical (electronic) properties [6,11].In order to develop insight into the genesis of helices/helicoids, we investigate an emblematic example of pattern formation, namely the formation of precipitation patterns in the wake of reaction-diffusion fronts [12,13]. The motivation for this choice comes from the observation that helicoidal structures have an axis, and the correlations are simple in the plane perpendicular to the axis. This suggests that building the perpendicular correlations in the wake of an advancing planar front may be a simple and natural mechanism of creating helices/helicoids. Additional motivation comes from the existence of a large body of knowledge in the related Liesegang phenomena [12,13]. It allows the use of well-established experimental and theoretical approaches, thus making it easier to develop a novel view on the formation of helical structures.Our main results concern the probabilistic aspects of the symmetry-breaking route. We determine the probability P H of the emergence of single helices/helicoids in Liesegang-type experiments as the conditions such as the initial concentration of inner or outer electrolytes, or the temperature are changed. P H is found to be well reproducible and large (P H > 0.5 for some parameter range). The results are understood by expanding and simulating a model of formation of precipitation patterns [14]...

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“…5,[28][29][30][31] In particular they can be used to measure reaction rates that would otherwise be impossible using conventional stopped-flow techniques. 5 Fluorescence lifetime images were acquired at 0, 1, 2.5 and 10 mm from the point of confluence (corresponding to average residence times of 108, 540, 1350 and 5400 ms) using multiphoton FLIM microscopy and resulting fluorescence decay profiles were fitted to a single exponential decay model ( Figure 2). As expected, the extracted decay times increase as the two species diffuse and bind near the center of the microchannel.…”

Section: Resultsmentioning

confidence: 99%

Analysis of DNA Binding and Nucleotide Flipping Kinetics Using Two-Color Two-Photon Fluorescence Lifetime Imaging Microscopy

et al. 2014

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Uracil DNA glycosylase (UNG) plays a key role in DNA maintenance via base excision repair (BER). Its role is to bind to DNA, locate unwanted uracil and remove it via a base flipping mechanism. To date, kinetic analysis of this complex process has been achieved using stoppedflow analysis but, due to limitations in instrumental dead-times, discrimination of the "binding" 2 and "base flipping" steps is compromised. Herein we present a novel approach for analyzing base flipping using a microfluidic mixer and two-color two-photon (2c2p) fluorescence lifetime imaging microscopy (FLIM). We demonstrate that 2c2p FLIM can simultaneously monitor both binding and base flipping kinetics within the continuous flow microfluidic mixer, with results showing good agreement with computational fluid dynamics simulations.INTRODUCTION.

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Reaction-diffusion dynamics: Confrontation between theory and experiment in a microfluidic reactor

Cited by 87 publications

References 9 publications

Influence of buoyancy-driven convection on the dynamics of A+B→C reaction fronts in horizontal solution layers

Influence of buoyancy-driven convection on the dynamics of A+B→C reaction fronts in horizontal solution layers

Probability of the Emergence of Helical Precipitation Patterns in the Wake of Reaction-Diffusion Fronts

Analysis of DNA Binding and Nucleotide Flipping Kinetics Using Two-Color Two-Photon Fluorescence Lifetime Imaging Microscopy

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