We propose a micromixer for obtaining better efficiency of vortex induced electroosmotic mixing of non-Newtonian bio-fluids at a relatively higher flow rate, which finds relevance in many biomedical and biological applications. To represent the rheology of non-Newtonian fluid, we consider the Carreau model in this study, while the applied electric field drives the constituent components in the micromixer. We show that the spatial variation of the applied field, triggered by the topological change of the bounding surfaces, upon interacting with the non-uniform surface potential gives rise to efficient mixing as realized by the formation of vortices in the proposed micromixer. Also, we show that the phase-lag between surface potential leads to the formation of asymmetric vortices. This behavior offers better mixing performance following the appearance of undulation on the flow pattern. Finally, we establish that the assumption of a point charge in the paradigm of electroosmotic mixing, which is not realistic as well, under-predicts the mixing efficiency at higher amplitude of the non-uniform zeta potential. The inferences of the present analysis may guide as a design tool for micromixer where rheological properties of the fluid and flow actuation parameters can be simultaneously tuned to obtain phenomenal enhancement in mixing efficiency.

Salinity energy generation (SEG) studies have only been done under isothermal conditions at ambient temperature. The production of salinity energy can be improved under non-isothermal conditions, albeit preserving the energy...

We investigate the contact-line dynamics of two immiscible fluids in a narrow fluidic confinement comprising wettability-gradient surfaces, where the bulk fluid motion is actuated by an externally applied electric field. We assume that the channel walls bear spatially uniform surface potential. Our analysis, based on the diffuse interface formalism, reveals that the contact line undergoes stick-slip motion over the chemical patches and its velocity is a strong function of the interfacial electrokinetics. We also show that the tendency of the contact line of getting pinned to the selected patches can decrease or increase with its progression along the channel, depending on the ratio of the permittivities of the two fluids. Finally, we establish the functional dependency of the time taken by the contact line to move across the patches (capillary filling time) on the combined consequences of interfacial electrochemistry and wettability patterning.

The salinity gradient energy or the ‘blue energy’ is one of the most promising inexpensive and abundant sources of clean energy, having immense capabilities to serve modern-day society. In this...

In this work, we present the theoretical investigation of the transient rotating electro-osmotic flow of a couple stress fluid in a microchannel, through the Laplace transform technique. The analysis is dependent on the Debye–Hückel linear approximation for electrical potentials. The governing equations of the couple stress fluid are taken to address the flow field in a rotating environment. The mathematical formulation of these governing equations provides a system of ordinary differential equations, which are then solved to achieve analytical solutions for electrostatic potential, axial and transverse velocity distribution, and volumetric flow rate. A comparison was made for the present analytical solution with data available in the literature. There was excellent matching. The characteristics of different influential parameters on axial and transverse velocity distributions, volume, and angle flow rates are pictorially deliberated. The study reveals that the rise in the couple stress parameter accelerates the axial electro-osmotic flow velocity inside the electrical double layer.

We propose a novel and efficient mixing technique in a soft narrow-fluidic channel under the influence of electrical forcing.

We consider electrically driven dynamics of an incompressible binary fluid, with contrasting densities and viscosities of the two phases, flowing through narrow fluidic channel with walls with predefined surface wettabilities. Through phase field formalism, we describe the interfacial kinetics in the presence of electro-hydrodynamic coupling and address the contact line dynamics of the two-fluid system. We unveil the interplay of the substrate wettability and the contrast in the fluid properties culminating in the forms of two distinct regimes—interface breakup regime and a stable interface regime. Through a parametric study, we demarcate the effect of the density and viscosity contrasts along with the electrokinetic parameters such as the surface charge and ionic concentration on the underlying contact-line-dynamics over interfacial scales.

We investigate the performance of layered graphene oxide (GO) membrane in forward osmosis (FO) process for seawater desalination via nonequilibrium molecular dynamics (MD) simulations. A 0.56 M NaCl solution is used as the feed solution and a mixture of 1.0 M MgCl2 and 0.05 M Al2(SO4)3 solution is used as a draw solution. The effect of internal structure of the layered GO membrane on its performance as a FO membrane is investigated by considering three different membrane configurations which differ in their pore offset distance W. The dynamics of the permeating water and ions through the layered GO membrane is also investigated. Increase in W reduces the water permeability of the layered GO membrane and increases its salt rejection. One of the reason for this could be the blockage of permeate pathways through the layered GO membrane due to the movement of the GO nanosheets. This becomes more prominent with increasing W. Increasing W also leads to increase in distance traversed by the permeating water molecule through the layered GO membrane while it decreases velocity of the same. This study also reveals that ion permeability is affected by the parameter W, type and magnitude of charge the ion possesses and the intensity of interaction between water molecules and the ion.