Department of Chemical Engineering

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Subject: search.filters.subject.Electroosmotic flow (EOF)

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    Hydrodynamics of electroosmotic flow in a microchannel with porous wall
    (2019-02) Bhattacharjee, Saikat
    Microchannel with porous wall has various microfluidic applications including iontophoresis, diagnostic devices, etc. In order to have an efficient and better design of such devices, exact quantification of velocity field in the microchannel needs to be established. In the present study, an analytical solution of velocity field in a microchannel with porous wall was obtained for a Newtonian fluid in case of a combined electroosmotic and pressure driven flow using perturbation technique. The velocity profile was reduced to well known solutions for three asymptotic cases, namely, purely electroosmotic flow and purely pressure driven flow in an impervious conduit as well as pressure driven flow with permeable wall. The pressure drop profile along the channel length was also generated. Effects of operating parameters, i.e., wall suction velocity, electrolyte concentration and channel half height on velocity and pressure fields were also investigated.
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    Effect of electrolyte nature in mass transport of a neutral solute in a microtube with porous wall
    (AIChE, 2019-08) Bhattacharjee, Saikat
    Electroosmotic flow in a microchannel is an active area in microfluidics. Microchannels with porous wall are advantageous due to selective separation and enhanced mass transport. An economic and innovative method to fabricate hollow microtubes and their application in electrokinetics are illustrated. Effects of asymmetric electrolyte on mass transport of a neutral macrosolute in the microtube with porous wall are investigated. The combined velocity profile including both pressure-driven and electroosmotic flow is modeled for different electrolytes. It is found from the study that the addition of higher valency asymmetric electrolyte (3:1) increases transport of neutral solutes across the porous wall compared to its symmetric counterpart (1:1). The developed model was validated with the experimental results, using a cartridge having hollow microtubes with porous wall. This study would be helpful to select an appropriate electrolyte, improving the design, and performance prediction of microfluidic devices.
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    Mass transfer of a neutral solute in polyelectrolyte grafted soft nanochannel with porous wall
    (Wiley, 2019-11) Bhattacharjee, Saikat
    A soft nanochannel involves a soft interface that contains a polyelectrolyte layer (PEL) sandwiched between a rigid surface and a bulk electrolyte solution. Mass transfer of a neutral solute in a combined electroosmotic and pressure driven flow through a polyelectrolyte grafted charged nanochannel with porous wall is presented in this work. Assuming the PEL as fixed charged layer and PEL-electrolyte interface as a semi-penetrable membrane, analytical solutions were obtained for potential distributions (for small wall potential). Velocity profiles were also derived in the same domains, for both inside and outside the PEL. Convective-diffusive species balance equation was semi-analytically solved inside the PEL. Expression of length averaged Sherwood number was also obtained and effects of different parameters, namely, drag parameter (α), Debye parameter urn:x-wiley:01730835:media:elps7092:elps7092-math-0001, and PEL thickness were studied in detail. The variation of permeate concentration and permeation flux across the porous wall was obtained.
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    Effects of finite ion size on transport of neutral solute across porous wall of a nanotube
    (Springer, 2020-07) Bhattacharjee, Saikat
    Effect of finite ion size on the transport of a neutral solute across the porous wall of a nanotube is presented in this study. Modified Poisson–Boltzmann equation without the Debye–Huckel approximation is used to determine the potential distribution within the tube. Power law fluid is selected for the study, as its rheology resembles closely to the real-life physiological fluids. The flow within the tube is actuated by the combined effects of pressure and electroosmotic forces. Steady-state solute balance equation is solved by the similarity technique in order to track the solute transport across the tube. The effects of ionic radius, ionic concentration, and flow behavioral index on the length-averaged Sherwood number, permeate flux, and permeate concentration are analyzed. This study will be extremely helpful in predicting the transport characteristics of a neutral solute in real physiological systems and also to fine-tune the performance of microfluidic devices having porous wall.