Nonlinear phenomena and qualitative evaluation of risk of clogging in a capillary microreactor under imposed electric field

Přibyl, Michal; Šnita, Dalimil; Marek, M.

doi:10.1016/j.cej.2004.10.003

Cited by 21 publications

(31 citation statements)

References 35 publications

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“…2,5,11,14 In their seminal work, Gálfi and Rácz 8 carried out an analytical calculation of the precipitate front properties through the coupling of diffusion to secondorder reaction kinetics (A + B f C). They found that the distance traveled by the front scales as t 1/2 , while the pulse width scales as t 1/6 and the rate of product formation as t -2/3 .…”

Section: Modelmentioning

confidence: 99%

Pulse-Front Propagation and Interaction During the Growth of CdS Nanoparticles in a Gel

2009

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We studied the spatiotemporal dynamics of a new system consisting of sulfide ions (outer electrolyte) diffusing into an organic gel (gelatin) containing mercaptoethanol-capped cadmium ions (inner electrolyte). The product, cadmium sulfide, exhibits a faint yellow transparent propagating front starting at the gel-outer electrolyte interface. When subjected to UV light, this system reveals fluorescing CdS nuclei localized spatially in a narrow region, called pulse, that leads the front and propagates down the tube. We show that the pulse consists of CdS nanoclusters of an average size of about 4 nm, whereas the trailing front consists of 6-8 nm cubic-phase CdS crystallites. The width of the pulse remains constant in time, t, at about 2 mm and independent of the outer concentration S0. It was found that the speed of the pulse fluctuates as the concentration of the capping agent is varied, with fastest pulses attained at a concentration of 40 mM for two different outer concentrations of sulfide ions. The origin of the yellow fluorescence of the pulse originates from emission from surface states. This dynamical system was then theoretically studied using a competitive particle growth model. The resulting evolution equations were solved numerically, and the results were compared to the experimental findings. It was shown that the model agrees in many aspects with the experiment. The densities of small particles and large particles rho were shown to evolve like a pulse and a front, respectively. The front was shown to extend "diffusively" as t1/2, as found experimentally. The distance traveled by the pulse xpeak was shown to increase with outer concentration S0 and obeys a concentration power law xpeak approximately S(0)1/4. The width w of the pulse also obeys a time power law w approximately ta with a crossover between early times (a=1/3) and intermediate times (a=0). This system would enable us to study the early time dynamics of Liesegang systems.

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Section: Modelmentioning

confidence: 99%

Pulse-Front Propagation and Interaction During the Growth of CdS Nanoparticles in a Gel

2009

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“…Thus, for nanochannel IEF, the Poisson-Nernst-Planck model [23][24][25] must be solved. However, in this study, the length scale of the electric double layer is three to four orders of magnitude smaller than the length scale of a typical microfluidic device used for IEF.…”

Section: A Governing Equationsmentioning

confidence: 99%

Effect of Joule heating on isoelectric focusing of proteins in a microchannel

2014

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Electric field-driven separation and purification techniques, such as isoelectric focusing (IEF) and isotachophoresis, generate heat in the system that can affect the performance of the separation process. In this study, a new mathematical model is presented for IEF that considers the temperature rise due to Joule heating. We used the model to study focusing phenomena and separation performance in a microchannel. A finite volume-based numerical technique is developed to study temperature-dependent IEF. Numerical simulation for narrow range IEF (6 < pH < 10) is performed in a straight microchannel for 100 ampholytes and two model proteins: staphylococcal nuclease and pancreatic ribonuclease. Separation results of the two proteins are obtained with and without considering the temperature rise due to Joule heating in the system for a nominal electric field of 100 V/cm. For the no Joule heating case, constant properties are used, while for the Joule heating case, temperature-dependent titration curves and thermo-physical properties are used. Our numerical results show that the temperature change due to Joule heating has a significant impact on the final focusing points of proteins, which can lower the separation performance considerably. In the absence of advection and any active cooling mechanism, the temperature increase is the highest at the midsection of a microchannel. We also found that the maximum temperature in the system is a strong function of the DpK value of the carrier ampholytes. Simulation results are also obtained for different values of applied electric fields in order to find the optimum working range considering the simulation time and buffer temperature. Moreover, the model is extended to study IEF in a straight microchip where pH is formed by supplying H þ and OH À , and the thermal analysis shows that the heat generation is negligible in ion supplied IEF. V C 2014 AIP Publishing LLC.

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“…Thus, for nanochannel free flow IEF, one has to solve the Poisson-Nernst-Planck model. 16,17 However, in this study, the length scale of the electric double layer is 3-4 orders of magnitude smaller than the length scale of typical microfluidic device used for FFIEF. Moreover, IEF channels are generally coated with chemicals to eliminate the electric double layer formation.…”

Section: B Ampholyte and Protein Net Chargementioning

confidence: 95%

Mathematical and numerical model to study two-dimensional free flow isoelectric focusing

et al. 2014

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Even though isoelectric focusing (IEF) is a very useful technique for sample concentration and separation, it is challenging to extract separated samples for further processing. Moreover, the continuous sample concentration and separation are not possible in the conventional IEF. To overcome these challenges, free flow IEF (FFIEF) is introduced in which a flow field is applied in the direction perpendicular to the applied electric field. In this study, a mathematical model is developed for FFIEF to understand the roles of flow and electric fields for efficient design of microfluidic chip for continuous separation of proteins from an initial well mixed solution. A finite volume based numerical scheme is implemented to simulate two dimensional FFIEF in a microfluidic chip. Simulation results indicate that a pH gradient forms as samples flow downstream and this pH profile agrees well with experimental results validating our model. In addition, our simulation results predict the experimental behavior of pI markers in a FFIEF microchip. This numerical model is used to predict the separation behavior of two proteins (serum albumin and cardiac troponin I) in a two-dimensional straight microchip. The effect of electric field is investigated for continuous separation of proteins. Moreover, a new channel design is presented to increase the separation resolution by introducing cross-stream flow velocity. Numerical results indicate that the separation resolution can be improved by three folds in this new design compare to the conventional straight channel design. V C 2014 AIP Publishing LLC.

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Nonlinear phenomena and qualitative evaluation of risk of clogging in a capillary microreactor under imposed electric field

Cited by 21 publications

References 35 publications

Pulse-Front Propagation and Interaction During the Growth of CdS Nanoparticles in a Gel

Pulse-Front Propagation and Interaction During the Growth of CdS Nanoparticles in a Gel

Effect of Joule heating on isoelectric focusing of proteins in a microchannel

Mathematical and numerical model to study two-dimensional free flow isoelectric focusing

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