Research Projects

The proposed research work will investigate the ion transport and secondary electroosmotic flow (EOF) phenomena of Newtonian/non-Newtonian fluids in conical micro conduits fitted with micro chambers of non-uniformly charged conductive surfaces for mixing satisfying Maxwell stress components. Particular emphasis will be given to the treatment of asymmetries in hydrophobic conical channels together with slip and no-slip boundary conditions to overcome the challenges and difficulties that arise in the fluid flow phenomena in organ-on-a-chip (OOC) devices. Analytical and numerical investigations will be performed over a wide range of flow properties, potential and ionic conditions to understand and control sample transport adjacent to rough or structured surfaces in small scales. A great deal of research has been done on EOFs, both numerically and experimentally, to visualize the flow behaviour using Newtonian and non-Newtonian fluids, both in electrolytes and salt-free solutions [Majhi & Nayak, 2022, Majhi et al., 2023]. However, very few studies are reported in the literature for EOF mixing with non-Newtonian fluid using micro chambers, which are of great importance in BioMEMS and Lab on Chip (LOC) operations. In this proposal, the mathematical model is based on the Poisson-Nernst-Planck and Navier-Stokes equations and is used to characterize the flow phenomena. This model depends on a series of assumptions such as the ions are considered as a point charge neglecting the finite size of ion, the permittivity and viscosity of the medium are assumed to be constant, non-Coulombic interaction between ions and the charged surface is disregarded, incomplete dissociation of the electrolyte is ignored. Because of this reason, the fluid-structure interaction exhibits some unstable behaviour in the case of a thick Debye layer with high surface charge density. Various mathematical models, such as the Carnahan-Starling model or the Boublik-Mansoori-Carnan-Starling-Lelan model, will be considered for finite size of ion, dielectric decrement, nonconstant permittivity, Coulombic interaction with non-uniform surface charge distribution due to which a nonlinear flow instability may occur in the nanopore. To account for this effect, a rigorous theoretical study is required to probe the effects of conical structures or roughness for hydrodynamic slips. The question for the slip models of wetting surfaces for measurement of unphysically considerable slip lengths and deviations near contact separations could be solved to enhance the shear effects and can be an influential factor for flow enhancement with pressure drop. Another question arises for the adsorbed mobile and immobile charges close to the interface and their relationships for the amplification of fluid transport. Hence, a detailed theoretical and numerical estimation is proposed to obtain the maximum ion transport due to high surface charge density to investigate the flow dynamics under a weak electric field.