Electroosmotic Research Articles

Streaming electric field, electroviscous effect, and electrokinetic liquid flows in the induced pressure-driven transport of active liquids in narrow capillaries.

In this paper, we develop a theory for studying the electrokinetic effects in a charged nanocapillary filled with active liquid. The active particles present within the active liquid are self-driven, demonstrate vortex defects, and enforce a circumferentially arranged polarization field. Under such circumstances, there is the development of an induced pressure-gradient-driven transport dictated (similar to diffusioosmotic transport) by the presence of an axial gradient in the activity (or the concentration of the active particles). This pressure-driven transport has a profile different from the standard Hagen-Poiseuille flow in a nanocapillary. Also, this induced pressure-driven flow drives electrokinetic effects, which are characterized by the generation of a streaming electric field, associated electroosmotic (EOS) transport opposing pressure-driven flow, and electroviscous effect. We quantify these effects as functions of dimensionless parameters that vary inversely as the strength of the activity-induced pressure-driven flow and salt concentrations. Overall, we anticipate that this paper will draw immense attention toward a new type of activity-induced pressure-driven flow and associated electrokinetic phenomena in charged nanoconfinements.

Electroosmotic permeability in kaolinite and CaCO3 poultice mixtures

Electrokinetic treatment of masonry for desalination or electroosmotic dewatering depends on a poultice, in which the electrodes are placed, which fulfills several purposes. Poultice composed of kaolinite and CaCO3 have been shown to have good workability and high pH buffering capacity. In this work, the electroosmotic (EO) permeability is studied in different kaolinite - CaCO3 mixtures. In addition, the effect on EO of using NaCl as a mixing solution is investigated. A special cell is used to test the EO in the specimens. A phenomenological approach, based on the potential gradient and the flux of solution, was used to calculate the EO flow rate and EO permeability coefficient. Results showed that by increasing the concentration of CaCO3 in the poultice mixture, the EO flow rate decreased and the poultice with 80 % CaCO3 and more did not have any EO flow. Furthermore, the ionic strength in the mixing solution decreases the EO flow rate.

Electrohydrodynamic (In)Stability of Microfluidic Channel Flows: Analytical Expressions in the Limit of Small Reynolds Number

We study electrohydrodynamic (EHD) linear (in)stability of microfluidic channel flows, i.e., the stability of interface between two shearing viscous (perfect) dielectrics exposed to an electric field in large aspect ratio microchannels. We then apply our results to particular microfluidic systems known as two-liquid electroosmotic (EO) pumps. Our novel results are detailed analytical expressions for the growth rate of two-dimensional EHD modes in Couette–Poiseuille flows in the limit of small Reynolds number (R); the expansions to both zeroth and first order in R are considered. The growth rates are complicated functions of viscosity-, height-, density-, and dielectric-constant ratio, as well as of wavenumbers and voltages. To make the results useful to experimentalists, e.g., for voltage-control EO pump operations, we also derive equations for the impending voltages of the neutral stability curves that divide stable from unstable regions in voltage–wavenumber stability diagrams. The voltage equations and the stability diagrams are given for all wavenumbers. We finally outline the flow regimes in which our first-order-R voltage corrections could potentially be experimentally measured. Our work gives insight into the coupling mechanism between electric field and shear flow in parallel-planes channel flows, correcting an analogous EHD expansion to small R from the literature. We also revisit the case of pure shear instability, when the first-order-R voltage correction equals zero, and replace the renowned instability mechanism due to viscosity stratification at small R with the mechanism due to discontinuity in the slope of the unperturbed velocity profile.

Modeling Zeta Potential for Nanoparticles in Solution: Water Flexibility Matters.

Nonequilibrium molecular dynamics simulations were performed to study the electrokinetic properties of five mainstream TIPxP water models (namely, TIP3P-FB, TIP3Pm, TIP4P-FB, TIP4P-Ew, and TIP4P/2005) in NaCl aqueous solutions in the presence of a negatively charged TiO2 surface. The impact of solvent flexibility and system geometry on the electro-osmotic (EO) mobility and flow direction was systematically assessed and compared. We found that lack of water flexibility decelerates the forward EO flow of aqueous solutions at moderate (0.15 M) or high (0.30 M) NaCl concentrations, in some special cases to such an extent that EO flow reversal occurs. Zeta potential (ZP) values were then determined from the bulk EO mobilities using the Helmholtz-Smoluchowski formula. The straight comparison against available experimental data strongly suggests that water flexibility improves the ZP determination of NaCl solutions adjacent to a realistic TiO2 surface under neutral pH conditions.

Influence of Nafion-Coating of Ag/Ag2O/C Electrodes on Long-Term Performance of an Electroosmotic Pump

Ag/Ag2O electrodes were fabricated on both carbon fiber paper (CP) and carbon fiber cloth (CC) substrates via galvanostatic electrodeposition to develop an electroosmotic (EO) pump. The results showed that Ag was deposited along the carbon fibers and further grew into Ag particles. The Ag loading on CP was higher than that of CC at the same current density, and the difference increased further with the current density increase. Nafion coating was applied on the as-electrodeposited Ag/Ag2O/CP electrode to prevent the degradation of Ag particles using dip coating, followed by drop coating. The Nafion-coated Ag/Ag2O/CP electrodes showed much better electroosmotic pump performance and long-term stability than the uncoated electrodes, revealing that the Nafion ionomer can enhance the proton conductivity and mitigate the degradation of Ag particles during the electrochemical reactions. The EO pumps built with Nafion-modified Ag/Ag2O/CP electrodes with an active area of 0.28 cm2 generated a maximum pressure of 157 kPa and a maximum flow rate of 28.21 ul min−1. The Postmortem analysis of the pumped working fluids collected from the EO pumps operated at a constant potential for three days was performed to further investigate the effects of Nafion coating on Ag degradation.

Specific Ion and Electric Field Controlled Diverse Ion Distribution and Electroosmotic Transport in a Polyelectrolyte Brush Grafted Nanochannel.

Controlling ion distribution inside a charged nanochannel is central to using such channels in diverse applications. Here, we show the possibility of using a charged polyelectrolyte (PE) brush-grafted nanochannel for triggering diverse nanoscopic ion distribution and nanofluidic electroosmotic transport by controlling the valence and size of the counterions (that screen the charges of the PE brushes) and the strength of an externally applied axial electric field. We atomistically simulate separate cases of fully charged polyacrylic acid (PAA) brush functionalized nanochannels with Na+, Cs+, Ca2+, Ba2+, and Y3+ counterions screening the PE charges. Four key findings emerge from our simulations. First, we find that the counterions with a greater valence and a smaller size prefer to remain localized inside the brush layer. Second, for the case where there is an added chloride salt with the same cation (as the screening counterions), there are more coions (Cl- ions) in the brush-free bulk than counterions (for counterions Na+, Ca2+, Ba2+, Y3+): this is a manifestation of the overscreening (OS) of the PE brush layer. Contrastingly, the number of Cs+ ions remain higher than the Cl- ions inside the brush-free bulk, ensuring that there is no OS effect for this case. Third, large applied electric field enables a few Na+, Cs+, and Ba2+ counterions to leave the brush layer and to go to the bulk: this makes the OS of the PE brush layer disappear for the cases of PE brushes being screened by the Na+ and Ba2+ ions. On the other hand, no such electric-field-mediated disappearance of OS is observed for the cases of Ca2+ and Y3+ screening counterions; we attribute this to the firm attachment of these counterions to the negatively charged monomers. Free energy associated with a counterion binding to a PE chain corroborates this diversity in the counterion-specific response to the applied electric field. Finally, we demonstrate that such diverse ion distributions, along with specific electric-field-strength-dependent ion properties, lead to (1) electroosmotic (EOS) transport in nanochannels grafted with PAA brushes screened with Cs+ ions to be always counterion dominated, (2) EOS transport in nanochannels grafted with PAA brushes screened with Ca2+ and Y3+ ions to be always coion-dominated, and (3) EOS transport in nanochannels grafted with PAA brushes screened with Na+ and Ba2+ ions to be coion dominated for smaller electric fields and counterion dominated for larger electric fields.

Enhancing electrokinetic soil flushing with air stripping for the treatment of soil polluted with phenol and o-chlorophenol

This paper describes the treatment of soil spiked with a mixture of phenol and o-chlorophenol in a bench-scale plant combining Electrokinetic Soil Flushing with Air Stripping (EKSF-AS). Results demonstrate that this combination can be a good alternative for the remediation of soils, although many initially unexpected results were found. Phenol and 2-clorophenol are transported to the cathode wells by dragging with the electroosmotic flow, where they are exhausted by stripping with air. A significant amount of both species reached the anode, where they are transformed by anodic oxidation into a mixture of hydroquinone and benzoquinone, which remains in the anolyte, not being further oxidized, transported to the cathode or dragged by the electro-osmotic (EO) flux (more than 58 and 66% of the initial pollution was transported from soil to anolyte well, respectively at 0.75 and 1.50 V cm−1). Injected pressurized air can haul an important part of the pollution (more than 25%) and nearly 95% of the pollution contained in the raw soil is depleted after 14 days of treatment.

Development of a High-Performance and Robust PANI:PSS/C Electrode for an Electroosmotic Pump

A high-performance and durable electroosmotic (EO) pump is developed by using electropolymerized PANI:PSS/C electrodes. PANI:PSS was electrochemically synthesized on the carbon fiber paper using cyclic voltammetry and characterized by a variety of physicochemical methods including field emission scanning electron microscopy (FESEM), electron probe microanalyzer (EPMA), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). There was a linear relationship with a regression coefficient R2 ≥ 0.97 between the applied potential and the peak current (Ipeak), maximum flow rate (Qmax), maximum pressure (Pmax), respectively. The EO pump built with PANI:PSS/C electrodes, with an active area of 1.0 cm2, generated the maximum stall pressure of 122 kPa and the maximum flow rate of 203 ul min−1 at 4 V by using deionized (DI) water as a working fluid. The EO pumps assembled with PANI:PSS/C electrodes showed much better overall performances than those made with the bare carbon paper and exhibited good long-term stability without substantial decay for 5 days of continuous operation even at a high potential of 4 V.

Electroosmotic flow of generalized fractional second grade fluid with fractional Cattaneo model through a vertical annulus

Because of the rapid advancement of microdevices technologies, electroosmotic flow (EOF) has gotten a lot of coverage in recent years. EOF has a range of benefits over other micropumps, including the ability to create continuous pulse-free flows and elimination of moving parts. Our aim is to investigate the unsteady electroosmotic flow (EOF) of an electrolyte solution of generalized fractional second grade hybrid nanofluid (Cu-TiO2/Water) confined between vertical two coaxial tubes. The energy equation will be altered by the fractional Cattaneo model. The finite Hankel technique and Laplace transformation will be employed to acquire the solution of the mathematical model. Since obtaining the inversion of Laplace of the transformed functions in the closed-form is a challenging task, the numerical inversion algorithm will be used. The results showed that the hybrid nanofluid became more viscous with increasing the volume concentration which reduces the electroosmotic (EO) velocity and the flow rate. Moreover, the electroosmotic flow is boosted by the free convection force.

Simultaneous Energy Generation and Flow Enhancement (Electroslippage Effect) in Polyelectrolyte Brush Functionalized Nanochannels.

Energy generation through nanofluidics is a topic of great nanotechnological relevance. Here, we conduct all-atom molecular dynamics (MD) simulations of the transport of water and ions in a pressure-driven flow in nanochannels grafted with charged polyelectrolyte (PE) brushes and discover the possibility of simultaneous electrokinetic energy generation and flow enhancement (henceforth denoted as the electroslippage effect). Such PE-brush-functionalized nanochannels have been recently shown to demonstrate an overscreening (OS) effect (characterized by the presence of a greater number of screening counterions within the PE brush layer than needed to screen the PE brush charges), a consequent presence of excess co-ions within the PE brush-free bulk, and a co-ion-driven electroosmotic (EOS) transport in the presence of small to moderate applied axial electric fields. In this study, however, we find that the streaming current, which represents the current generated by the flow-driven downstream advection of the charge imbalance present within the electric double layer (EDL) that screens the PE brush charges, is governed by the migration of the counterions. This stems from the fact that the highest contribution to the overall streaming current arises from the region near the PE brush-water interface (where there is an excess of counterions), while the brush-free bulk yields a hitherto unreported, but small, co-ion-dictated streaming current. This downstream advection of the charge imbalance (and the resultant counterion-driven streaming current) eventually leads to the development of an electric field (streaming electric field) in the direction that is opposite the direction of the counterion-driven streaming current. The streaming current and the streaming electric field interact to generate the electrokinetic energy. Equally important, this streaming electric field induces an EOS transport, which becomes co-ion-driven, due to the presence of excess co-ions in the brush-free bulk. For the case of nanochannels grafted with negatively charged PE brushes, the streaming electric field will be in a direction that is opposite that of the pressure-driven transport, and hence the co-ion (or anion) driven EOS flow will be in the same direction as the pressure-driven transport. On the other hand, for the case of nanochannels grafted with positively charged PE brushes, the streaming electric field will be in the same direction as the pressure-driven flow, and hence the co-ion (or cation) driven EOS flow, will again be in the same direction as the pressure-driven flow. Therefore, whenever there occurs a presence of the OS and the resulting co-ion-driven EOS transport in PE brush grafted nanochannels, regardless of the sign of the charges of the PE brushes, this EOS transport will always aid the pressure-driven transport and will cause the most fascinating increase in the net volume flow rate across the nanochannel cross section, which is the electroslippage effect.

PH-Mediated Aggregation-to-Separation Transition for Colloids Near Electrodes in Oscillatory Electric Fields.

Colloids in low-frequency (<1 kHz) oscillatory electric fields near planar electrodes aggregate in neutral pH electrolytes due to electrohydrodynamic (EHD) flow but separate in alkaline pH electrolytes. Colloid ζ-potential and electrolyte ion mobilities are thought to play roles in the underlying mechanism for this phenomenon, but a unifying theory for why particles aggregate in some electrolytes and separate in others remains to be established. Here, we show that increasing local pH near the electrode with an electrochemical reaction causes a colloidal aggregation-to-separation transition in oscillatory electric fields that induce strong attractive EHD flows. An electroactive molecule, para-benzoquinone, was electrochemically reduced at the electrode to locally increase the solution pH near the colloids. Superimposing a sufficiently large steady electrochemical potential onto an oscillatory potential caused a reversible aggregation-to-separation transition. Counterintuitively, decreasing frequency, which increases attractive EHD drag forces, caused a similar aggregation-to-separation transition. Even more interesting, multiple transitions were observed while varying the oscillatory potential. Taken together, these results suggested that the oscillatory potential induced a repulsive hydrodynamic drag force. Scaling arguments for the recently discovered asymmetric rectified electric field (AREF) showed that a repulsive AREF-induced electroosmotic (EO) flow competed with attractive EHD flow. A pairwise colloidal force balance including these competing flows exhibited flow inversions qualitatively consistent with experimentally observed aggregation-to-separation transitions. Broadly, these results emphasize the importance of AREF-induced EO flows in colloid aggregation and separation in low-frequency oscillatory electric fields.

Thermo-osmotic transport in nanochannels grafted with pH-responsive polyelectrolyte brushes modelled using augmented strong stretching theory

Abstract

The influence of skin barrier impairment on the iontophoretic transport of low and high molecular weight permeants

The effect of skin barrier impairment on the iontophoretic transport of low (acetaminophen (ACM), lidocaine (LD), ketorolac (KT)) and high molecular weight permeants, (cytochrome c (Cyt c) and ribonuclease T1 (RNase T1)), was evaluated using tape-stripping (TS) and fractional laser ablation for “large-scale” and “localized” barrier disruption. Interestingly, removal of the stratum corneum did not invariably lead to an increase in iontophoretic delivery of the permeants. Decrease of electroosmotic (EO) flow and facilitated transport of Cl- ions in the cathode-to-anode direction, which reduced cation electromigration (EM), both impacted cation delivery by anodal iontophoresis but the effects were partly offset by enhanced passive diffusion. Decrease in EO increased cathodal iontophoresis of KT but not that of RNase T1. Permeability coefficients confirmed the superiority of EM over EO for small molecules, LD > KT > ACM. A combination of fractional laser ablation and iontophoresis was advantageous for both positively and negatively charged small molecules as passive penetration was significantly enhanced. In conclusion, results demonstrated that (i) skin ablation prior to anodal iontophoresis decreased EO and EM but could be advantageous for delivery if the ablative technique enhanced passive penetration thereby compensating reduction of electrotransport and (ii) reduced EO favored cathodal electrotransport.

Theoretical study on the massively augmented electro-osmotic water transport in polyelectrolyte brush functionalized nanoslits.

We demonstrate that functionalizing nanoslits with pH-responsive polyelectrolyte brushes can lead to extremely fast electro-osmotic (EOS) water transport, where the maximum centreline velocity and the volume flow rate can be an order of magnitude larger than these quantities in identically charged brush-free nanochannels for a wide range of system parameters. Such an enhancement is most remarkable given that the brushes have been known to retard the transport by imparting additional drag on the fluid flow. We argue that this enhancement stems from the localization of the charge density of the brush-induced electric double layer (and, hence, the EOS body force) away from the nanochannel wall (or the location of the wall-induced drag force). This ensures a much larger impact of the EOS body force triggering such fast water transport. Finally, the calculated flux values for the present brush-grafted nanochannels are found to be significantly larger than those for a wide range of nanofluidic membranes and channels, suggesting that the brush functionalization can be considered as a mechanism for enabling such superfast nanofluidic transport.

Remediation of inorganic contaminants in soil using electrokinetics, phytoremediation techniques

During the last decade, the expansion of urbanization and industrial activities caused serious environmental problems such as soil pollution. Currently, the vast majority of remediation projects involve disposing of contaminated soil in a landfill. With the introduction of this, cause increased landfill tax and becoming less desirable, and so robust. Novel technologies are required to remediate soil contamination with toxic contaminants, including heavy metals and organic pollutants. Electrokinetic (EK) and Phytoremediation are better techniques. Electrokinetic is an emerging remediation technology for mixed contaminants, especially in low hydraulic conductivity soils. During the electrokinetic remediation process, an electric field is applied to the specimen to remove the contaminants from soil by means of electro-osmotic (EO), electromigration (EM), and electrophoresis (EP) processes. This paper addresses the problem of contaminants in soil and has investigated the use of electrokinetic phenomena and phytoremediation as tools to bring about an increase in this factor, leading to improved degradation. Electrokinetic separation is an emerging technology that relies on the application of a low-density, the direct current through the soil to separate and extract the heavy metal. When comparing these two techniques a significant increase in the effectiveness of the remediation was noted with electrokinetics technique, with substantially faster degradation to occur.

The electrokinetic properties of cationic surfactants adsorbed on a hydrophobic substrate: effect of chain length and concentration

Electrokinetic (EK) properties, such as the electro-osmotic flow (EOF), are influenced by surfactant adsorption at the solid–liquid interface. With the growing popularity of poly(methyl methacrylate) (PMMA) as the substrate for polymeric-based microfluidics, it is important to understand the effect of surfactants on EOF in these devices. Here, we investigate the effect of surfactant chain length and concentration on the electro-osmotic (EO) mobility induced by three cationic surfactants cetyl trimethylammonium bromide (CTAB), trimethylammonium bromide (TTAB), dodecyl trimethylammonium bromide (DTAB) in PMMA microcapillaries. The EO mobility curve as a function of concentration shows three regimes. First, at very low concentrations below 0.002 mM, the mobility is constant and approximately equal to the value obtained with the surfactant-free electrolyte (1 mM KCl). Next, the EOF reverses and mobility increases linearly with surfactant concentration. Finally, the mobility reaches a plateau at a concentration well below surfactant CMC (0.2-mM CTAB, 0.5-mM TTAB and 2-mM DTAB) and decreases at the vicinity of CMC. Our results show that the rate of change in mobility with respect to concentration is a linear function of chain length and increases with longer-chain surfactants. In addition, we deduce the magnitude of Van der Waals or cohesive energy between the adsorbed alkyl chains from the EO mobility values. For the alkyl trimethylammonium surfactants adsorbed on the hydrophobic surface of PMMA, this energy was found to be 0.114 kT smaller than the reported value for ionic surfactants adsorbed on a hydrophilic surface.

Unsteady rotating electroosmotic flow with time-fractional Caputo-Fabrizio derivative

As an effective driven mechanism proved experimentally, rotating electroosmotic (EO) micropump has attracted the attentions of many researchers in recent years. In this article, an exact solution of transient rotating EO flow with time-fractional Caputo-Fabrizio derivative through a slit microchannel is obtained by using Laplace transform method. It is interesting to find from computational results that with the increase of fractional parameter α (0<α<1), the time required to attain steady velocity becomes shorter and the oscillating phenomenon becomes more pronounced.

Dynamic control of capillary flow in porous media by electroosmotic pumping.

Microfluidic paper-based analytical devices (μPADs) rely on capillary flow to achieve filling, mixing and delivery of liquids. We investigate the use of electroosmotic (EO) pumping as a mechanism for dynamic control of capillary flow in paper-based devices. The applied voltage can accelerate or decelerate the baseline capillary-driven velocity, as well as be used to create a tunable valve that reversibly switches the flow on and off in an electrically controlled manner. The method relies on simple fabrication and allows repeated actuation, providing a high degree of flexibility for automation of liquid delivery. We adapt the Lucas-Washburn model to account for EO pumping and provide an experimentally validated analytical model for the distance penetrated by the liquid as a function of time and the applied voltage. We show that the EO-pump can reduce filling time by 6.5-fold for channels spanning several cm in length, relative to capillary filling alone. We demonstrate the utilization of the EO-pump for a tunable and dynamic flow control that accelerates, decelerates and stops the flow on demand. Finally, we present the use of the EO-pump for fluid flow sequencing on a paper-based device.

Electro-osmotic pumping through a bumpy microtube: Boundary perturbation and detection of roughness

To machine precision, a micro-duct cannot be fabricated without producing surface roughness. It is of essential importance to examine the effects and predict the level of roughness on electro-osmotic (EO) pumping for ducts of fundamental shapes. In this study, we consider a bumpy microtube with its wall shape modeled by the product of two sinusoidal functions. Boundary perturbation is carried out with respect to the amplitude roughness ε (relative to the Debye length) up to the second-order by considering the Debye-Hückel approximation and viscous Stokes equation for the electrolyte transport. Besides the amplitude roughness ε, the key parameters include the azimuthal wave number n and the axial wave number α of the bumpiness, as well as the non-dimensional electrokinetic width K. It is shown that the EO pumping rate Q is modified by a second-order term −ε2πχ, namely, Q = Q0 − ε2πχ, where Q0 denotes the pumping rate through the smooth tube. The net effect χ = χ1 + χ2 comprises two components: χ1 = χ1(K) &amp;lt; 0 increases with increasing K, representing a pure gain, while χ2 has no definite sign and is a complex function of K, n, and α. In particular, χ is negative at small α whilst being positive at large α, and the dividing line of signs also depends on K. For small α (&amp;lt;1), χ increases with increasing n at all K, while for large α (&amp;gt;1), χ decreases with increasing n at large K (&amp;gt;20). For a given number of oscillations Ac = nα (&amp;gt;1), there exists an intermediate n at which the EO pumping rate is maximized at small K (&amp;lt;20). Moreover, we identify a long-wavelength limit singularity in the EO pumping rate as α → 0 for all n, i.e., in the longitudinal sense. In addition, the velocity component along the tube axis is modified by a second-order term of the roughness, though the same velocity component near the wavy wall exhibits periodic behaviors in phase with the wall roughness. Physical reasoning is given to all the derived mathematical results, and their implication in practical applications as a model for predicting tube roughness is explained. As the tube shape represents a conduit of practical use, a particular emphasis is placed upon potential applications of the derived result.

Ionic Diffusoosmosis in Nanochannels Grafted with End-Charged Polyelectrolyte Brushes.

In this paper, we develop a theory to study the imposed axial salt-concentration-gradient-driven ionic diffusioosmosis (IDO) in soft nanochannels or nanochannels grafted with end-charged polyelectrolyte (PE) brushes. Our analysis first quantifies the diffusioosmotically induced electric field, which is primarily dictated by the imposed concentration gradient (CG) with little contribution of the induced osmosis. This induced electric field triggers an electroosmotic (EOS) transport, while the net diffusioosmotic (DOS) transport results from a combination of this EOS transport and a chemiosmotic (COS) transport arising from the pressure gradient induced by the applied CG. Our results demonstrate that the DOS transport is massively enhanced in nanochannels grafted with PE brushes with weak grafting density stemming from the significantly enhanced EOS transport caused by the localization of the EOS body force away from the nanochannel walls. This augmentation is even stronger for cases where the COS transport aids the EOS transport. On the other hand, the DOS transport gets severely reduced in nanochannels grafted with dense PE brushes owing to the severity of the brush-induced additional drag force. We anticipate that these findings will help to unravel an entirely new understanding of induced electrokinetic transport in soft nanochannels.