Electrokinetic Energy Conversion Research Articles

Non-Monotonic Variation in the Streaming Potential in Polyelectrolyte Grafted Nanochannels Mediated by Ion Partitioning Effects

BackgroundPolyelectrolyte grafted ‘soft’ nanochannels are known to enhance electrokinetic energy conversion efficiency, paving the way for a sustainable energy harvesting mechanism. However, the true potential of their efficacy remains to be tapped, as attributed to a deficit in accounting for the interplay between solution pH and ion partitioning effect arising due to permittivity contrast between the coated layer and the bulk media, leading to predictions of an erroneous ionic distribution and a wrongly estimated electrokinetic response. ResultsWe unravel the electrokinetic behavior of a pH-regulated zwitterionic polyelectrolyte layer grafted nanofluidic system. To this end, we derive a detailed theoretical formulation that considers the nuanced interplay between solution pH and the ion partitioning effect through a thermodynamically consistent ionic distribution. Here, for the first time, we demonstrate a non-monotonic trend in the streaming potential with an increase in the ion partitioning effect, in contrast to a monotonic increase as reported previously. Additionally, we identify a critical permittivity ratio specific to the solution pH at which maximum streaming potential can be obtained. SignificanceWe shed light on the counterintuitive effect borne from the increased ion partitioning effect, unveiling a hitherto hidden facet of electrokinetics. By elucidating the delicate balance between solution pH, ion partitioning effect, and polyelectrolyte charge, our findings offer a comprehensive understanding of the multifaceted interplay shaping soft-electrokinetic systems, thereby paving the way for transformative advancements in energy conversion technologies.

Unsteady electroosmotic flow of Carreau–Newtonian fluids through a cylindrical tube

The present study aims to investigate the fully developed electroosmotic flow of Carreau-Newtonian fluids within a circular tube, considering two different boundary conditions of zeta potential. The unsteady behaviour of Carreau-Newtonian fluids, is attributed to the pulsatile pressure-driven flow. Studying two distinct formulations, slip and no-slip zeta potentials, illustrates the relative movement of fluid particles and the charged surface. The proposed study’s framework is divided into two regions: a central region containing a non-Newtonian Carreau fluid exhibiting both shear-thinning and thickening behaviour, and a peripheral region containing a Newtonian fluid with the effect of an electrical double layer at the solid wall of the cylindrical tube. The Poisson–Boltzmann equation under the assumption of Debye–Hückel approximation governs the potential distribution due to the electric double layer, facilitating the examination of electroosmotic flow through tube. Obtaining analytical solutions for the momentum equations in both regions becomes challenging due to the inclusion of pulsatile pressure-driven flow and a non-Newtonian Carreau fluid. Asymptotic series expansions are employed, utilizing small parameters such as the Weissenberg number (We≪1) and a pulsatile Reynolds number (α≪1), to derive velocity expressions for both regions. Wall shear stress fluctuations, as indicated by time-averaged wall shear stress and oscillatory shear index are assessed to gauge the temporal variation of wall shear stress from the dominant blood flow direction. By utilizing potential and hydrodynamic variables, an asymptotic formulation for the streaming potential is developed to ascertain the asymptotic expression of electrokinetic energy conversion efficiency and scrutinize the impacts of pertinent physical parameters on it. The proposed study prominently shows that the Debye–Hückel parameter, Weissenberg number, pulsatile Reynolds number, and time-dependent pressure gradient significantly influence the fluid velocity, flow rate, and flow resistance. The notable determination of the present study is that the velocity amplitude and electrokinetic energy conversion efficiency are enlarged in the slip-dependent case relative to the no-slip zeta potential. It is noteworthy that as inertial forces become more prominent compared to viscous forces, both time-average wall shear stress and oscillatory shear index experience a slight decrease, although the reduction in oscillatory shear index is minimal owing to the absence of obstruction within the tube wall. The NDSolve numerical scheme in Mathematica software is employed to calculate numerical solutions for the governing equations, which are subsequently verified against results obtained through asymptotic analysis. The findings of this study are expected to deepen our understanding of unsteady electroosmotic flows of Carreau fluid and contribute to the design and development of advanced microfluidic devices with enhanced performance for various applications.

Effect of solvent depletion on electrokinetic energy conversion in viscoelastic fluids

We analyze the electrokinetic energy conversion from the pressure-driven flow of viscoelastic fluids akin to dilute polymer solutions. In contrast to the previously reported results, we account for the reduced differential capacitance over the interfacial layer and the solvent-mediated non-electrostatic interactions, cumulatively represented in an extended continuum framework. We attribute a physical basis of our consideration from the perspective of the formation of a polymer-depleted layer at the channel interface, where the explicit role of the solvent appears to dictate the electromechanics–hydrodynamics coupling over the interfacial scales. By adapting a “box-model” depicting the alterations in the solvent permittivity across the interfacial layer and accommodating a non-electrostatic interaction coefficient concomitantly, the interfacial electrokinetics are coupled with the bulk flow of the polymer-rich medium using the simplified Phan-Thien–Tanner (sPTT) constitutive model. A closed-form theory is obtained that includes only two fitting parameters, namely, the span of the interfacial layer and the strength of the non-electrostatic interactions. These parameters are estimated from comprehensive molecular simulation data. The results of the investigation are analytically tractable and enable rationalizing the “electrokinetic” implications of the polymer-depleted interfacial layer and the possibility that the electrokinetic parameters can be extracted from measurements obtained from experiments. This paves the way toward optimizing the induced streaming potential for the conversion of hydraulic energy to electrical power in polymeric solutions.

Streaming Potential and Associated Electrokinetic Effects through a Channel Filled with Electrolyte Solution Surrounded by a Layer of Immiscible and Dielectric Liquid.

The present article deals with the streaming potential-mediated pressure-driven flow across a channel in which the electrolyte solution is surrounded by a layer of cell membrane. Such a membrane of a biological cell may be modeled as an immiscible and dielectric liquid, which may bear free lipid molecules or charged surfactants. The presence of such additional charged molecules may lead to formation of liquid-liquid interfacial charge. In addition, the dielectric gradient-mediated ion partitioning effect further plays an important role in two-phase electrokinetic motion. We aim to study the generation of streaming potential and electrokinetic conversion efficiency as well as associated electroviscous effect for the undertaken problem. The mathematical model is based on the Poisson-Boltzmann equation for electrostatic potential and the Stokes equation for fluid flow, and the problem is studied considering suitable interfacial conditions for the flow variables along the liquid-liquid interface. The explicit analytical results for velocity and streaming field, electrokinetic energy conversion efficiency, and the parameter indicating the electroviscous effect are derived under the Donnan limit and within the Debye-Hückel electrostatic framework. We further numerically calculated the aforementioned intrinsic electrokinetic parameter associated with the problem undertaken for a wide range of pertinent parameters. The results are illustrated to indicate the impact of pertinent parameters on the generation of the streaming potential and associated electrokinetic effects.

Electrokinetic energy conversion and desalination of an asymmetric nanopore with applied temperature gradients

The electrokinetic energy conversion (EKEC) and desalination performance of a cation-selective funnel-shaped nanopore are investigated theoretically through a continuum description. The effects of pore geometry, characterized by a symmetric factor between the conical and the cylindrical regions, are considered along with pressure and temperature gradients. A desalination index is proposed to evaluate the performance of desalination, examining the trade-off between the ion rejection rate and the volumetric flow rate. It is found that applying a positive (or negative) ∆T relative to ∆P lowers (or raises) the rejection rate, as influenced by the ion selectivity. In addition, the rejection rate at a positive pressure difference (∆P>0; flow coming from tip to base) is slightly larger than that at ∆P<0 because the former has a stronger inlet electric field. Based on the desalination index, a positive ∆T manifests a better desalination performance than a negative ∆T, in contrast to the EKEC case, which displays better energy efficiency under a negative ∆T than under a positive ∆T. The smaller diffusivity of Na+ compared with K+ makes the power density and efficiency of NaCl better than those of KCl. Meanwhile, the more significant thermal diffusion for NaCl impacts its rejection rate more appreciably.

Streaming potential of viscoelastic fluids with the pressure-dependent viscosity in nanochannel

The plane Poiseuille flow of viscoelastic fluids with pressure-dependent viscosity is analyzed through a narrow nanochannel, combining with the electrokinetic effect. When the fluid viscosity depends on pressure, the common assumption of unidirectional flow is unsuitable since the secondary flow may exist. In this case, we must solve the continuity equation and two-dimensional (2D) momentum equation simultaneously. It is difficult to obtain the analytical electrokinetic flow characteristics due to the nonlinearity of governing equations. Based on the real applications, we use the regular perturbation expansion method and give the second-order asymptotic solutions of electrokinetic velocity field, streaming potential, pressure field, and electrokinetic energy conversion (EKEC) efficiency. The result reveals a threshold value of Weissenberg number (Wi) exists. The strength of streaming potential increases with the pressure-viscosity coefficient when Wi is smaller than the threshold value. An opposite trend appears when Wi exceeds this threshold value. Besides, the Weissenberg number has no effect on the zero-order flow velocity, but a significant effect on the velocity deviation. A classical parabolic velocity profile transforms into a wavelike velocity profile with the further increase in Wi. Finally, the EKEC efficiency reduces when pressure-dependent viscosity is considered. Present results are helpful to understand the streaming potential and electrokinetic flow in the case of the fluid viscosity depending on pressure.

Electrokinetic energy conversion efficiency in a nanochannel with slip-dependent zeta potential

Abstract Electrokinetic energy conversion in hydrophobic nanochannels has been studied by many scholars because of its high estimated conversion efficiency. However, these studies mainly focued on the the case of slip-independent zeta potential, ignoring the effect of slip length on zeta potential. In the paper, we study the energy conversion of pressure-driven flow in plane nanochannel with slip-dependent (S.D.) zeta potential. Through the derived analytical expression and schematic analysis of electrokinetic energy conversion efficiency, it can be observed that, within specific parameter ranges, when taking into account the S.D. zeta potential, the conversion efficiency is improved. The maximum conversion efficiency obtained is approximately 23%, which is an improvement of 5.9% compared to the slip-independent (S.I.) zeta potential. This study may have a positive impact on achieving more efficient energy collection and play a important role in the energy field.

Electrokinetic energy conversion of nanofluids in porous microtubes with Green’s function

Abstract Micro-devices fabrication has led to extensive scientific research on microfluidics and microelectromechanical systems. These devices are used for a wide range of technological applications, but research on microfluidic devices for nanofluids is relatively scarce. In response to this problem, the electrokinetic energy conversion (EKEC) efficiency of nanofluids is provided under the coupling effect of pressure gradient and magnetic field through porous microtubes using the Debye–Hückel linearization and the Green’s function method. The results show that the periodic excitation of the square waveform is more effective in increasing the EKEC efficiency. In addition, compared with previous studies, the average velocity is in good agreement with the cosine waveform at R = 0.2. It is worth noting that compared to cosine waves, the average velocity reaches 47% in triangular waves and 85% in square waves.

Multi-objective optimization of electrokinetic energy conversion efficiency and entropy generation for streaming potential driven electromagnetohydrodynamic flow of couple stress Casson fluid in microchannels with slip-dependent zeta potentials

The present study develops a new mathematical approach to the pressure-mediated streaming potential flow of couple-stress Casson fluids with the influence of slip-dependent zeta potential between two parallel plates in a microchannel. The lateral electric and transverse magnetic fields are externally applied to control the fluid flow. A multi-objective optimization technique was implemented by utilizing the non-dominated sorting genetic algorithm (NSGA-II) by varying different constraints to maximize the electrokinetic energy conversion efficiency and minimize the irreversibility of the system. The present results show that the couple stress and Casson parameters influence the development of streaming potential, electrokinetic energy conversion (EKEC) efficiency, temperature, Nusselt number, and Bejan number for asymmetric velocity slip and temperature jump circumstances. The viscous dissipation, Joule heating, and thermal radiation parameters significantly affect the heat transfer. According to the present results, the EKEC efficiency increases with a slip-dependent zeta potential of couple stress Casson fluid, couple stress fluid, Casson fluid, and Newtonian fluid by 45.92 %, 47.10 %, 42.81 %, and 37.68 %, respectively, compared to that for the slip-independent zeta potential. At the centre of the microchannel for the jump boundary conditions, temperature increases by 2.95 % compared to no jump boundary conditions.

Pressure-driven electrokinetic energy conversion in conical nanochannels with ion concentration polarization

Electrokinetic energy conversion (EEC) in nanochannels subject to a large pressure gradient (or difference) is affected appreciably by the ion concentration polarization (ICP). The current literature only addresses the ICP effects on EEC in nanochannels with uniform cross-sections, such as cylindrical nanochannels. Here, we adopt a numerical approach which couples the Poisson, Nernst–Planck, and Navier–Stokes equations to perform a detailed analysis of the pressure-driven EEC in nanochannels with varying cross-sections (i.e., conical nanochannels) under the ICP effect. The results reveal that two pressure gradients of the same magnitude but opposite directions can produce regulation effects on the EEC and ICP: under large values of the pressure gradient and surface charge density, a forward pressure gradient (e.g., the pressure gradient driving the fluid flow from the tip to the base of the nanochannel) leads to more nonlinear current-voltage (I-V) curves than a reverse pressure gradient (e.g., the pressure gradient driving the fluid flow from the base to the tip of the nanochannel); however, a forward pressure gradient produces weaker ICP than a reverse pressure gradient. These two opposite regulation behaviors suggest that the nonlinearity of I-V curves and the ICP is negatively interrelated, in contrast to the case of cylindrical nanochannels. Moreover, increasing nanochannel conicity enhances the nonlinearity of I-V curves but weakens the ICP effects, further confirming the negative interrelationship between the ICP and nonlinear I-V curves. This study clarifies the interrelationship between ICP and nonlinear I-V curves and is of practical significance for EEC device design and operation.

Optimizing energy generation in power-law nanofluid flow through curved arteries with gold nanoparticles

The investigation of blood flow into curved arteries is fascinating and essential to prevent the advancement of vascular disease. Motivated by electro-kinetic manipulation, gold nanoparticles, and their size applications, a mathematical model is developed to explain blood flow, entropy generation, and electro-kinetic energy conversion (EKEC) efficiency in curved arterial flow. To make this study more realistic, a patient-specific overlapped stenosis condition and non-Newtonian (power-law fluid) blood flow model have been considered. The effects of a magnetic field, external heating, and chemical reactions are also included. The Stone’s strongly implicit scheme has been considered to solve the system of non-linear partial differential equations (PDE’s) in the” MATLAB” software. In this numerical investigation, an error tolerance of has been considered for every iteration step under Stone’s scheme. The significance of various physical parameters, such as nanoparticle volume fraction (m), their size (dp), magnetic field intensity (M), inverse Debye length (), flow behavior index (Sc), heat source (H), and chemical reaction parameter (ξ) on the blood flow velocity, temperature, concentration, EKEC efficiency, and entropy generation have been explained graphically. This study also developed stream function contours to describe flow trapping patterns. The findings of this study conclude that the blood flow EKEC efficiency reduces with the presence of nanoparticles and stenosis in the artery. In addition, both flow velocity and entropy enhance by adopting large-size nanoparticles instead of small diametric nanoparticles. Clinical researchers and biologists may use the results of this computational study to forecast endothelial cell damage and plaque deposition in curved arteries with WSS profiles, by which the severity of these conditions can be reduced.

Characterization of liquid flow and electricity generation in a glass channel based evaporation-driven electrokinetic energy conversion device

Evaporation-driven spontaneous capillary flow presents a promising approach for driving electrolytes through electrically charged channels and pores in electrokinetic energy conversion devices. However, there are no literature reports of detailed flow visualization in these systems and/or experimental observations relating the liquid velocity and evaporation rate to the generated voltage and current. In this manuscript, we describe such a visualization study for a glass channel based electrokinetic energy conversion device with one of its channel terminals left open to ambient air for facilitating the evaporation process. Fluorescence microscopy was used to measure the liquid velocity in the electrokinetic energy conversion channel by observing the advancement of an electrolyte solution dyed with a neutral tracer. The accumulation of the same dye tracer was also imaged at the open terminal of this glass conduit to estimate the rate of solvent evaporation, which was found to be consistent with the flow velocity measurements. Additionally, an electrochemical analyzer was employed to record the electrical voltage and current produced by the device under different operating conditions. The highest electrical power output was derived in our experiments upon flowing de-ionized water through a 1 μm deep channel, which also produced the fastest liquid velocity in it. Moreover, the energy conversion efficiency of our device was observed to increase for shallower channels and lower ionic strength electrolytes, consistent with previous literature reports on electrokinetic energy conversion platforms.

Ionic Flexible Mechanical Sensors: Mechanisms, Structural Engineering, Applications, and Challenges

AbstractThis review covers the evolution of flexible mechanical sensors from an “electronic” language to an “ionic” language, which provides key reference information for the development of next‐generation bio‐intelligent sensing devices. Unlike sensors that rely solely on electron modulation, the core feature of the ionic flexible mechanical sensor (IFMS) is the ability of mechanical deformation to induce ion transport and compensation, thus demonstrating their conceptual similarity to biomechanical strain systems. Here, the basic design principles of flexible mechanical sensors modulated by ion transport are highlighted. This review provides a detailed description of the mechanotransduction mechanisms of IFMS devices based on ion transport modulation. First, although with similar mechanisms to conventional flexible mechanical sensors via piezoresistive, piezoelectric, and triboelectric transduction mechanisms, the core driver for IFMS devices is ions (not electrons). In addition, the transduction models and principles of action of novel transduction mechanisms that have been explored in the last decade are described in detail, which include interfacial iontronic sensing and potentiometric and electrokinetic energy conversion. According to the characteristics of the device, the relevant structural engineering is further highlighted. A comprehensive review of important IFMS application approaches (human–machine interfaces, life and health applications) is presented. Importantly, future challenges and possible solutions for IFMS devices are presented based on the existing research.

Electrokinetic energy conversion in nanochannels with surface charge-dependent slip

Electrokinetic energy conversion in nanochannels has attracted increasing attention in recent years. However, few scholars have studied the impact of the intrinsic distinction between surface charge-dependent and independent slip on power generation performance. In this work, we consider three kinds of boundary conditions, including no slip, independent slip and surface charge-dependent slip, to investigate the ion concentration distribution, velocity and energy conversion performance in nanochannels combined with the electric double layer theory. The results show that the boundary slip can improve the output performance significantly. Besides, due to the restriction of surface charge on boundary slip, the power generation performance under independent slip and dependent slip exhibits a significant deviation. Thus, the independent slip model is not suitable for predicting ion transport and fluidic flow in practical applications. Moreover, the ion concentration and channel height also play an optimizing role in the performance of electrokinetic energy conversion. We find the boundary slip is a benefit to promote the ion flux due to the velocity mechanism but has little effect on ion concentration distribution. The findings of this study can help for better understanding the ion transfer behavior in nanochannels, which provides useful information for the design and optimization of nanochannel power generation.

Electrokinetic energy conversion of high pressure-driven flow with pressure-viscosity effect at high zeta potential

In this study, the electrokinetic energy conversion efficiency is investigated theoretically in high pressure-driven flow with the pressure-viscosity effect. Calculations of the electrokinetic flow in a straight nanochannel are based on the Poisson-Boltzmann equation and modified fluid momentum equation. Once the viscosity of fluid is dependent on the pressure, the strongly non-linear governing equation should be solved simultaneously due to the unknown fluid viscosity. Thus, the domain perturbation method is used to solve the distributions of flow velocity and pressure. Based on obtained velocity and pressure, the maximum conversion efficiency is calculated by thermodynamic analysis. Results show the maximum efficiency increases with the decrease of salt concentration and the peak efficiency can be obtained at sufficiently low salt concentration. For a given salt concentration, the maximum efficiency decreases monotonously with the increase of pressure-viscosity coefficient. Besides, the maximum energy conversion efficiency of ignoring the pressure-viscosity effect is larger than that of considering the pressure-viscosity effect.

Electrokinetic energy conversion in the nanochannel coupled with surface charge and slip effects

Inspired by the universal phenomena in nature and advances in nanotechnology, the ion transport in nanochannel receives increasing attention and shows great promising in energy conversion. The precedent studies generally predicted the ion transport by tuning the single physical parameter, the understanding of ion dynamics in the real multi-physical coupling systems is still scarce. Here, an ion transport model coupled with surface charge and slip effects is proposed to investigate the energy conversion behavior in nanochannel. The results show that the surface charge density increases with the increasing bulk concentration, nanochannel size and solution pH. The original boundary slip tends to decrease the surface charge density and the surface charge in turn reduces the boundary slip significantly, which manifests the strong coupling effect of diverse factors. The output power and energy conversion efficiency increases first and then decrease with the increasing bulk concentration and pH. The increase of channel size is beneficial for promoting output power, but unfavorable on energy conversion efficiency. More important, the boundary slip greatly enhances the output power and energy conversion efficiency, leading to a maximum output power and energy conversion efficiency is 2.7 pW and 30%, respectively. As a proof of concept, this work shows the distinct deviation in power generation in ion nanochannel with the constant and dependent physical property, providing the useful information to guide the design of real fluidic energy devices.

The electrokinetic energy conversion analysis of Newtonian fluids with pressure-dependent viscosity in rectangular nanotube

In this work, a theoretical analysis for the streaming potential and the electro-kinetic energy conversion (EKEC) efficiency of Newtonian fluids with pressure-dependent viscosity in rectangular nanotube was developed. Accordingly, the dimensionless velocity, dimensionless streaming potential, dimensionless pressure and the electrokinetic energy conversion (EKEC) efficiency are obtained by using the perturbation method expanded in terms of the pressure-viscosity coefficient based on a linear dependent relationship between viscosity and pressure. The results indicate that with pressure-viscosity coefficient, the pressure required to drive the flow increases sharply. Also as pressure-viscosity coefficient increases, the streaming potential and EKEC efficiency decreases gradually, contrary to velocity. It is worth noting that within the given parameter range, the maximum efficiency obtained by present analysis is about 0.19% when pressure viscosity coefficients is 0.001. Moreover, appropriately adjusting ratio of channel width to height and the geometrical aspect ratio of the nanotube can improve effectively the streaming potential and the EKEC efficiency.

Surface-charge-mobility-modulated electrokinetic energy conversion in graphene nanochannels

In recent years, electrokinetic energy conversion for pressure-driven flow through hydrophobic nanochannels has attracted increasing attention from numerous researchers. However, the reported electrokinetic energy conversion efficiencies may be overestimated owing to neglect of the surface charge mobility effect of hydrophobic nanochannels. In fact, both the effective slip length and the induced streaming potential are influenced by the surface charge mobility. In this paper, a theoretical model for electrokinetic energy conversion through graphene nanochannels is developed with consideration of the influence of surface charge mobility. The surface charge density σs varies from very low to considerably high. A numerical solution to the electric potential is obtained by using the finite difference method. We also derive analytical solutions for two limiting cases, namely, the case with a low zeta potential and the case without considerable electric double layer overlap. Our results reveal that consideration of the surface charge mobility leads to a 44% reduction in the maximum conversion efficiency. The predicted maximum efficiency is approximately 5.9% at σs = −0.0162 C/m2. Our results may prove useful for predicting and optimizing the electrokinetic conversion efficiency in hydrophobic nanochannels.

Analyses of electrokinetic energy conversion for periodic electromagnetohydrodynamic (EMHD) nanofluid through the rectangular microchannel under the Hall effects

Abstract Two-dimensional electromagnetohydrodynamic behavior of nanofluids through rectangular microchannels is investigated. The combined effects of time-periodic pressure gradients and magnetic fields in terms of the Hall effects on nanofluid flow are considered. Under the Debye–Hückel linearization approximation, the semi-analytic solution of the velocity field is derived by Green’s function method. Furthermore, the semi-analytic solutions of electrokinetic energy conversion (EKEC) efficiency and the streaming potential of nanofluids through the rectangular microchannels are obtained. The variations of the velocity, streaming potential, and EKEC efficiency with the electric double layer thickness K, Hartmann number Ha, Hall parameter m, and dimensionless frequency Ω are shown and briefly discussed.

The Impacts of Viscoelastic Behavior on Electrokinetic Energy Conversion for Jeffreys Fluid in Microtubes.

In this paper, the electrokinetic energy conversion (EKEC) efficiency, streaming potential of viscoelastic fluids in microtubes under an external transversal magnetic field, and an axial pressure gradient are investigated. The Jeffreys fluid is applied to model the viscoelastic fluid, and the analytic solution of velocity field is obtained using the Green’s function method. The influence of different dimensionless parameters, for instance, the Deborah numbers De and De*, which are related to the relaxation time and retardation time, respectively; the dimensionless electro-kinetic width K; the dimensionless frequency ω; the volume fraction of the nanoparticles φ and the dimensionless Hartmann number Ha; and three different imposed axial periodic pressure gradients (cosine, triangular, and square) on fluid dynamics are discussed. The physical quantities are graphically described, and the influence of different parameters on the EKEC is analyzed. The results indicate that De promotes the streaming potential and EKEC efficiency of the microtube, while De* inhibits them.