Electrokinetics of non-Newtonian fluids in poly-electrolyte grafted nanochannels: Effects of ion-partitioning and confinement

Paul, Rajorshi; Maity, Damodar; Agrawal, Pranshu; Bandopadhyay, Aditya; Chakraborty, Suman

doi:10.1016/j.jnnfm.2020.104348

Cited by 11 publications

(2 citation statements)

References 67 publications

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“…The parameters in the equation are defined as follows: μ p denotes the plastic viscosity, τ o represents the yield stress, m p represents a model parameter indicating stress growth, and denotes the strain rate, which is defined by the following equation γ̇ = 1 2 [ ∇ u + ( ∇ u ) normalT ] …”

Section: Theorymentioning

confidence: 99%

Ionic Transport Behavior of Soft Nanochannels for Newtonian and Non-Newtonian Electrolytes

Seifollahi,

Khatibi,

Ashrafizadeh

2024

Ind. Eng. Chem. Res.

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With the rapid progress in micro/nanofluidics, understanding the fundamental mechanisms of ionic transport, fluid behavior, and microsystem dynamics is more crucial than ever. Given the substantial expenses associated with manufacturing such systems, computational simulations offer a cost-effective avenue for advancing this industry sector while minimizing financial burdens. In this context, the current study explores the impact of electrolyte characteristics by numerically analyzing electroosmotic flow (EOF) in a conical nanochannel featuring charged slippery surfaces coated with a polyelectrolyte layer. Two types of electrolytic fluids, namely, water (representing a Newtonian fluid) and blood plasma (representing a non-Newtonian fluid), were investigated. The behavior of non-Newtonian electrolytes was modeled using the Bingham−Papanastasiou model. The governing equations of this nonlinear model, namely, the Poisson−Nernst−Planck and Navier−Stokes equations, were solved using the finite element method. Various parameters including slip length, surface charge density, soft layer charge density, and electrolyte concentration were systematically adjusted to assess three key aspects: EOF, ionic selectivity, and current rectification. The findings revealed that increasing the slip length significantly enhanced the EOF for both types of electrolytes. For instance, the EOF for platelets within the nanochannel core increased by 1.5 times with a slip length extension from 0 to 10 nm. Additionally, applying a positive voltage to the nanochannel amplified the EOF, particularly when the wall and soft layer charges were similar. For example, decreasing the wall charge density from 0 to −0.02 C/m 2 while applying a positive voltage led to a 1.5-fold increase in platelet EOF, rising from 0.028 to 0.042 m/s.

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Section: Theorymentioning

confidence: 99%

Ionic Transport Behavior of Soft Nanochannels for Newtonian and Non-Newtonian Electrolytes

Seifollahi,

Khatibi,

Ashrafizadeh

2024

Ind. Eng. Chem. Res.

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“…Barman et al 50 studied the modulation of EOF through a soft nanochannel considering power-law background electrolytic medium. Paul et al 51 theoretically analyzed the EOF of a non-Newtonian electrolyte in a soft nanochannel. Their study revealed that electrokinetic parameters are influenced by the fluid rheology and nanochannel properties, which impact the energy conversion efficiency.…”

Section: ■ Introductionmentioning

confidence: 99%

Electroosmotic Flow Modulation and Enhanced Mixing through a Soft Nanochannel with Patterned Wall Charge and Hydrodynamic Slippage

Pal,

Mahapatra,

Ohshima

et al. 2024

Ind. Eng. Chem. Res.

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The present study deals with the modulation of electroosmotic flow (EOF) through a soft nanochannel filled with a non-Newtonian fluid. The supporting charged hydrophobic walls of the channel are physicochemically patterned, which in turn leads to possibilities of modulated interfacial slip and surface ζ-potential. In addition, the supporting walls are grafted with an ion-and fluid-penetrable polyelectrolyte layer (PEL), which further entraps ionizable functional groups that give rise to immobile volumetric charges across the PEL. The fluid flow across such engineered devices under an applied electric field gives rise to an intricate electrohydrodynamic coupling over small scales. The mathematical model that describes the modulation of EOF across such a soft nanochannel comprises the Poisson equation for electrostatic potential and Nernst−Planck equations for conservation of the mass of mobile electrolyte ions, the flow field within the PEL is governed by a modified Darcy−Brinkman equation, and the Cauchy momentum equation governs the fluid flow outside the PEL. We adopt a radial basis function (RBF)based meshless computation scheme to simulate the set of governing equations. We further deduced analytical expressions for the electrostatic potential and velocity field for a Newtonian electrolyte through a bare channel with patterned surface potential, valid for a low charge limit. The numerical results are, however, obtained for a wide range of pertinent parameters and are further validated with the deduced theoretical results and available mathematical and experimental results from the literature. We observe an array of counter-rotating vortices that form in the flow field of the background non-Newtonian power-law fluid. Such vortices originate due to spatially periodic variations of hydrodynamic slippage as well as surface ζ-potential. The strength of vortices further intensifies due to the presence of the PEL grafted along the supporting rigid walls. The flow modulation across such a channel is illustrated by considering all of the possible sets of pertinent parameters. We further studied the impact of the rotational flow profile on the mixing of injected uncharged solutes. We observed that the formation of vortices in the flow field across the engineered soft nanochannel significantly affects the mixing efficiency, which can further be enhanced by suitably regulating the physicochemical and hydrodynamic parameters that control the flow modulation across the channel.

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Non-monotonic variation in the streaming potential in polyelectrolyte grafted nanochannels mediated by ion partitioning effects

Patwari,

Kumar,

Bakli

et al. 2024

Analytica Chimica Acta

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Electrokinetics of non-Newtonian fluids in poly-electrolyte grafted nanochannels: Effects of ion-partitioning and confinement

Cited by 11 publications

References 67 publications

Ionic Transport Behavior of Soft Nanochannels for Newtonian and Non-Newtonian Electrolytes

Ionic Transport Behavior of Soft Nanochannels for Newtonian and Non-Newtonian Electrolytes

Electroosmotic Flow Modulation and Enhanced Mixing through a Soft Nanochannel with Patterned Wall Charge and Hydrodynamic Slippage

Non-monotonic variation in the streaming potential in polyelectrolyte grafted nanochannels mediated by ion partitioning effects

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