NAREN BAG

@mnnit.ac.in

Assistant Professor, Department of Mathematics
Motilal Nehru National Institute of Technology Allahabad

NAREN BAG


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https://researchid.co/narenbag

RESEARCH INTERESTS

Computational Fluid Dynamics, Effect of Viscoplastic Fluids on Electrokinetic Phenomena, Microfluidics and Nanofluidics
10

Scopus Publications

192

Scholar Citations

7

Scholar h-index

7

Scholar i10-index

Scopus Publications

  • Electrophoresis of soft particles in a non-Newtonian power-law fluidic microenvironment
    Naren Bag, Komal Singh, Sankar Sarkar, Hiroyuki Ohshima, Partha Pratim Gopmandal
    Physics of Fluids, 2025
    The core-shell structured soft particles resemble various classes of bioparticles and environmental entities. The presence of the functional group within the peripheral soft layer may lead to volumetric charge distribution. Besides, depending on the Brinkmann screening length, the shell layer allows penetration of electrolyte ions, and thus, the classical ζ-potential loses its meaning for such composite particles and comprehensive study on the electrophoretic motion of such particles is required. Considering the importance, we made a systematic study on the electrophoresis of pH-regulated soft particles suspended in non-Newtonian background buffer solution. For such a case the coupling between electrostatics and non-Newtonian fluid rheological behavior complicates the particle motion. The widely used power-law model is adopted to consider the non-Newtonian behavior of background buffer solution. Going beyond the Debye–Hückel electrostatic framework, we have obtained numerical results for electrophoretic velocity of soft particles. We have further deduced analytical results for the electrophoretic velocity under various electrostatic and hydrodynamic limits. The impact of pertinent parameters on the particle motion in a non-Newtonian background solution is further illustrated. The magnitude in particle velocity is significantly high when the background fluidic medium is shear thinning in nature, however it reduces with the rise in flow behavior index due to enhanced viscous effect of the background medium. In addition, the impact of pertinent parameters is prominent on the electrophoretic velocity of the particle when the Brinkmann screening length of the peripheral shell layer is large, and their impact further decays with the reduction in Brinkmann screening length.
  • Impact of pH-Regulated Wall Charge on the Modulation of Electroosmotic Flow and Transport of Ionic Species through Slit Nanochannels
    Naren Bag
    Colloid Journal, 2023
    This article deals with the modulation of electroosmotic flow through narrow confinement. We consider the slit nanochannel in which the channel walls bear pH-regulated charge density, which further depends on the physicochemical properties of the microenvironment. We consider the general diffusive-electromigration-convective model for the transport of ionized liquid. The flow field is governed by the Navier−Stokes equation with an electromotive body force term. The electrostatic potential is governed by the Poisson equation. Going beyond the widely employed Debye−Hückel approximation, we have developed a sophisticated numerical tool based on the finite volume method to simulate the governing non-linear equations in an iterative manner. We have further derived closed form expressions for axial velocity and electrostatic potential within the Debye−Hückel framework, valid for weakly charged cases and for the entire possible range of bulk pH. Such an analytical expression is however useful for the accurate measurement of electrohydrodynamic behavior of flow characteristics across the slit nanochannel. Considering a wide range, the numerically obtained results are further discussed to show the impact of pertinent parameters.
  • Surface and zeta potentials of charged permeable nanocoatings
    Elena F. Silkina, Naren Bag, Olga I. Vinogradova
    Journal of Chemical Physics, 2021
    An electrokinetic (zeta) potential of charged permeable porous films on solid supports generally exceeds their surface potential, which often builds up to a quite high value itself. Recent work provided a quantitative understanding of zeta potentials of thick, compared to the extension of an inner electrostatic diffuse layer, porous films. Here, we consider porous coatings of thickness comparable to or smaller than that of the inner diffuse layer. Our theory, which is valid even when electrostatic potentials become quite high and accounts for finite hydrodynamic permeability of the porous materials, provides a framework for interpreting the difference between values of surface and zeta potentials in various situations. Analytic approximations for the zeta potential in the experimentally relevant limits provide a simple explanation of transitions between different regimes of electro-osmotic flows and also suggest strategies for its tuning in microfluidic applications.
  • Electro-osmotic properties of porous permeable films
    Elena F. Silkina, Naren Bag, Olga I. Vinogradova
    Physical Review Fluids, 2020
    Permeable porous coatings on a flat solid support significantly impact its electrostatic and electrokinetic properties. Existing work has focused on simplified cases, such as weakly charged and/or thick porous films, with limited theoretical guidance. Here, we consider the general case of coatings of any given volume charge density and obtain analytic formulas for electrostatic potential profiles, valid for any film thickness and salt concentration. They allow us to calculate analytically the difference between potentials at solid support and at interface with an outer electrolyte, that is the key parameter ascertaining the functionality of permeable coatings. Our analysis provides a framework for interpreting and predicting specific for porous films super-properties, from an enhanced ion absorption to a giant amplification of electro-osmotic flows. The results are relevant for hydrogel and zeolite coatings, porous carbon and ion-exchange resins, polyelectrolyte brushes, and more.
  • Achieving large zeta-potentials with charged porous surfaces
    Olga I. Vinogradova, Elena F. Silkina, Naren Bag, Evgeny S. Asmolov
    Physics of Fluids, 2020
    We discuss an electro-osmotic flow near charged porous coatings of a finite hydrodynamic permeability, impregnated with an outer electrolyte solution. It is shown that their electrokinetic (zeta) potential is generally augmented compared to the surface electrostatic potential, thanks to a large liquid slip at their surface emerging due to an electro-osmotic flow in the enriched by counter-ion porous films. The inner flow shows a very rich behavior controlled by the volume charge density of the coating, its Brinkman length, and the concentration of added salt. Interestingly, even for a relatively small Brinkman length, the zeta-potential can, in some cases, become huge, providing a very fast outer flow in the bulk electrolyte. When the Brinkman length is large enough, the zeta-potential could be extremely high, even at practically vanishing surface potential. To describe the slip velocity in a simple manner, we introduce a concept of an electro-osmotic slip length and demonstrate that the latter is always defined by the hydrodynamic permeability of the porous film and also, depending on the regime, either by its volume charge density or by the salt concentration. These results provide a framework for the rational design of porous coatings to enhance electrokinetic phenomena, and for tuning their properties by adjusting bulk electrolyte concentrations, with direct applications in microfluidics.
  • Enhanced electroosmotic flow of Herschel-Bulkley fluid in a channel patterned with periodically arranged slipping surfaces
    Somnath Bhattacharyya, Naren Bag
    Physics of Fluids, 2019
    In this paper, we consider the electroosmotic flow (EOF) of a viscoplastic fluid within a slit nanochannel modulated by periodically arranged uncharged slipping surfaces and no-slip charged surfaces embedded on the channel walls. The objective of the present study is to achieve an enhanced EOF of a non-Newtonian yield stress fluid. The Herschel-Bulkley model is adopted to describe the transport of the non-Newtonian electrolyte, which is coupled with the ion transport equations governed by the Nernst-Planck equations and the Poisson equation for electric field. A pressure-correction-based control volume approach is adopted for the numerical computation of the governing nonlinear equations. We have derived an analytic solution for the power-law fluid when the periodic length is much higher than channel height with uncharged free-slip patches. An agreement of our numerical results under limiting conditions with this analytic model is encouraging. A significant EOF enhancement and current density in this modulated channel are achieved when the Debye length is in the order of the nanochannel height. Flow enhancement in the modulated channel is higher for the yield stress fluid compared with the power-law fluid. Unyielded region develops adjacent to the uncharged slipping patches, and this region expands as slip length is increased. The impact of the boundary slip is significant for the shear thinning fluid. The results indicate that the channel can be cation selective and nonselective based on the Debye layer thickness, flow behavior index, yield stress, and planform length of the slip stripes.In this paper, we consider the electroosmotic flow (EOF) of a viscoplastic fluid within a slit nanochannel modulated by periodically arranged uncharged slipping surfaces and no-slip charged surfaces embedded on the channel walls. The objective of the present study is to achieve an enhanced EOF of a non-Newtonian yield stress fluid. The Herschel-Bulkley model is adopted to describe the transport of the non-Newtonian electrolyte, which is coupled with the ion transport equations governed by the Nernst-Planck equations and the Poisson equation for electric field. A pressure-correction-based control volume approach is adopted for the numerical computation of the governing nonlinear equations. We have derived an analytic solution for the power-law fluid when the periodic length is much higher than channel height with uncharged free-slip patches. An agreement of our numerical results under limiting conditions with this analytic model is encouraging. A significant EOF enhancement and current density in this modu...
  • Enhanced electroosmotic flow and ion selectivity in a channel patterned with periodically arranged polyelectrolyte-filled grooves
    S. Bhattacharyya, Naren Bag
    Microfluidics and Nanofluidics, 2019
  • Electroosmotic flow of a non-Newtonian fluid in a microchannel with heterogeneous surface potential
    Naren Bag, S. Bhattacharyya
    Journal of Non Newtonian Fluid Mechanics, 2018
  • Electroosmotic flow reversal and ion selectivity in a soft nanochannel
    Naren Bag, S. Bhattacharyya, Partha P. Gopmandal, H. Ohshima
    Colloid and Polymer Science, 2018
  • Enhanced Electroosmotic Flow Through a Nanochannel Patterned With Transverse Periodic Grooves
    S. Bhattacharyya, Naren Bag
    Journal of Fluids Engineering Transactions of the ASME, 2017
    In this paper, we have analyzed an enhanced electroosmotic flow (EOF) by geometric modulation of the surface of a charged nanochannel. Otherwise, flat walls of the channel are modulated by embedding rectangular grooves placed perpendicular to the direction of the applied electric field in a periodic manner. The modulated channel is filled with a single electrolyte. The EOF within the modulated channel is determined by computing the Navier–Stokes–Nernst–Planck–Poisson equations for a wide range of Debye length. The objective of the present study is to achieve an enhanced EOF in the surface modulated channel. A significant enhancement in average EOF is found for a particular arrangement of grooves with the width of the grooves much higher than its depth and the Debye length is in the order of the channel height. However, the formation of vortex inside the narrow grooves can reduce the EOF when the groove depth is in the order of its width. Results are compared with the cases in which the grooves are replaced by superhydrophobic patches along which a zero shear stress condition is imposed.

RECENT SCHOLAR PUBLICATIONS

  • Electrophoresis of soft particles in a non-Newtonian power-law fluidic microenvironment
    N Bag, K Singh, S Sarkar, H Ohshima, PP Gopmandal
    Physics of Fluids 37 (2) , 2025
    2025
    Citations: 3
  • Impact of pH-Regulated Wall Charge on the Modulation of Electroosmotic Flow and Transport of Ionic Species through Slit Nanochannels
    N Bag
    Colloid Journal, 1-11 , 2023
    2023
    Citations: 6
  • Surface and zeta potentials of charged permeable nanocoatings
    EF Silkina, N Bag, OI Vinogradova
    The Journal of Chemical Physics 154 (16), 164701 , 2021
    2021
    Citations: 10
  • Electro-osmotic properties of porous permeable films
    EF Silkina, N Bag, OI Vinogradova
    Physical Review Fluids 5 (12), 123701 , 2020
    2020
    Citations: 14
  • Achieving large zeta-potentials with charged porous surfaces
    OI Vinogradova, EF Silkina, N Bag, ES Asmolov
    Physics of Fluids 32 (10), 102105 , 2020
    2020
    Citations: 24
  • Enhanced electroosmotic flow of Herschel-Bulkley fluid in a channel patterned with periodically arranged slipping surfaces
    S Bhattacharyya, N Bag
    Physics of Fluids 31 (7), 072007 , 2019
    2019
    Citations: 30
  • Enhanced electroosmotic flow and ion selectivity in a channel patterned with periodically arranged polyelectrolyte-filled grooves
    S Bhattacharyya, N Bag
    Microfluidics and Nanofluidics 23 (3), 46 , 2019
    2019
    Citations: 12
  • Enhanced Electroosmotic Flow and Ion Selectivity of Newtonian/Non-Newtonian Fluids in Surface Modulated Microchannels or Soft Channels
    N Bag
    IIT Kharagpur , 2019
    2019
  • Electroosmotic flow of a non-Newtonian fluid in a microchannel with heterogeneous surface potential
    N Bag, S Bhattacharyya
    Journal of Non-Newtonian Fluid Mechanics , 2018
    2018
    Citations: 58
  • Electroosmotic flow reversal and ion selectivity in a soft nanochannel
    N Bag, S Bhattacharyya, PP Gopmandal, H Ohshima
    Colloid and Polymer Science, 1-11 , 2018
    2018
    Citations: 28
  • Effect of pH-Dependent Surface Charge on the Electroosmotic Flow through Nanochannel
    PP Gopmandal, S Bhattacharyya, N Bag
    World Academy of Science, Engineering and Technology, International Journal … , 2017
    2017
  • Transport of Analytes under Mixed Electroosmotic and Pressure Driven Flow of Power Law Fluid
    N Bag, S Bhattacharyya, PP Gopmandal
    World Academy of Science, Engineering and Technology, International Journal … , 2017
    2017
    Citations: 1
  • Enhanced electroosmotic flow through a nanochannel patterned with transverse periodic grooves
    S Bhattacharyya, N Bag
    Journal of Fluids Engineering , 2017
    2017
    Citations: 6

MOST CITED SCHOLAR PUBLICATIONS

  • Electroosmotic flow of a non-Newtonian fluid in a microchannel with heterogeneous surface potential
    N Bag, S Bhattacharyya
    Journal of Non-Newtonian Fluid Mechanics , 2018
    2018
    Citations: 58
  • Enhanced electroosmotic flow of Herschel-Bulkley fluid in a channel patterned with periodically arranged slipping surfaces
    S Bhattacharyya, N Bag
    Physics of Fluids 31 (7), 072007 , 2019
    2019
    Citations: 30
  • Electroosmotic flow reversal and ion selectivity in a soft nanochannel
    N Bag, S Bhattacharyya, PP Gopmandal, H Ohshima
    Colloid and Polymer Science, 1-11 , 2018
    2018
    Citations: 28
  • Achieving large zeta-potentials with charged porous surfaces
    OI Vinogradova, EF Silkina, N Bag, ES Asmolov
    Physics of Fluids 32 (10), 102105 , 2020
    2020
    Citations: 24
  • Electro-osmotic properties of porous permeable films
    EF Silkina, N Bag, OI Vinogradova
    Physical Review Fluids 5 (12), 123701 , 2020
    2020
    Citations: 14
  • Enhanced electroosmotic flow and ion selectivity in a channel patterned with periodically arranged polyelectrolyte-filled grooves
    S Bhattacharyya, N Bag
    Microfluidics and Nanofluidics 23 (3), 46 , 2019
    2019
    Citations: 12
  • Surface and zeta potentials of charged permeable nanocoatings
    EF Silkina, N Bag, OI Vinogradova
    The Journal of Chemical Physics 154 (16), 164701 , 2021
    2021
    Citations: 10
  • Impact of pH-Regulated Wall Charge on the Modulation of Electroosmotic Flow and Transport of Ionic Species through Slit Nanochannels
    N Bag
    Colloid Journal, 1-11 , 2023
    2023
    Citations: 6
  • Enhanced electroosmotic flow through a nanochannel patterned with transverse periodic grooves
    S Bhattacharyya, N Bag
    Journal of Fluids Engineering , 2017
    2017
    Citations: 6
  • Electrophoresis of soft particles in a non-Newtonian power-law fluidic microenvironment
    N Bag, K Singh, S Sarkar, H Ohshima, PP Gopmandal
    Physics of Fluids 37 (2) , 2025
    2025
    Citations: 3
  • Transport of Analytes under Mixed Electroosmotic and Pressure Driven Flow of Power Law Fluid
    N Bag, S Bhattacharyya, PP Gopmandal
    World Academy of Science, Engineering and Technology, International Journal … , 2017
    2017
    Citations: 1
  • Enhanced Electroosmotic Flow and Ion Selectivity of Newtonian/Non-Newtonian Fluids in Surface Modulated Microchannels or Soft Channels
    N Bag
    IIT Kharagpur , 2019
    2019
  • Effect of pH-Dependent Surface Charge on the Electroosmotic Flow through Nanochannel
    PP Gopmandal, S Bhattacharyya, N Bag
    World Academy of Science, Engineering and Technology, International Journal … , 2017
    2017