Digital flow control of electroosmotic pump: Onsager coefficients and interfacial parameters determination

Xu, Zuli; Miao, Jianying; Wang, Ning; Wen, Weijia; Sheng, Ping

doi:10.1016/j.ssc.2010.12.040

Cited by 13 publications

(19 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In order to check the flow rates, we always measure the reverse process-the streaming potential-as well. The agreement of the Onsager coefficients of the two EK processes (as required by microscopic reversibility) to within 10% not only ensured the accuracy of the measurements, but can also yield the ζ potentials of our samples as well as pinpoint the large interfacial conductivity of the Stern layer as a culprit in lowering the efficiency [12].…”

Section: B Experimental Setup and Measurementsmentioning

confidence: 52%

“…It has been shown that the surface conductivity [12] can be an obstacle in achieving an efficiency of >1%. Thus, further work in understanding and reducing surface conductivity is necessary for enhancing the EOP efficiency.…”

Section: Discussionmentioning

confidence: 99%

“…The ζ potential for the AAO samples has previously been measured to be -42 mV. In the same process, we can also determine the surface conductivity of the silicon wafer sample to be 0.33 nS [12]. Figure 2 shows the data for the silicon wafer samples.…”

Section: Digital Control Of Flow Ratementioning

confidence: 93%

“…We have developed a digital approach to control the flow rate in EOPs in which voltage pulses were used with different duty cycles [12]. The square wave amplitude and duration of the voltage pulse were 15 V and 1 ms, respectively.…”

Section: Digital Control Of Flow Ratementioning

confidence: 99%

See 3 more Smart Citations

Maximum efficiency of the electro-osmotic pump

Miao

Wang

et al. 2011

Phys. Rev. E

Self Cite

View full text Add to dashboard Cite

Electro-osmotic effect in a porous medium arises from the electrically charged double layer at the fluid-solid interface, whereby an externally applied electric field can give rise to fluid flow. The electro-osmotic pump (EOP) is potentially useful for a variety of engineering and biorelated applications, but its generally low efficiency is a negative factor in this regard. A study to determine the optimal efficiency of the EOP and the condition(s) under which it can be realized is therefore of scientific interest and practical importance. We present the results of a theoretical and experimental study on the maximum efficiency optimization of the electrokinetic effect in artificially fabricated porous media with controlled pore diameters. It is shown that whereas the EOP efficiency increases with decreasing channel diameter, from 4.5 to 2.5 μm for samples fabricated on oxidized silicon wafers as expected for the interfacial nature of the electro-osmotic effect, the opposite trend was observed for samples with much smaller channel diameters fabricated on anodized aluminum oxide films, with the pore surface coated with silica. These results are in agreement with the theoretical prediction, based on the competition between interfacial area and the no-slip flow boundary condition, that an optimal efficiency of ∼1% is attained at a microchannel diameter that is five times the Debye length, with a zeta potential of ∼100 mV.

show abstract

Section: B Experimental Setup and Measurementsmentioning

confidence: 52%

Section: Discussionmentioning

confidence: 99%

Section: Digital Control Of Flow Ratementioning

confidence: 93%

Section: Digital Control Of Flow Ratementioning

confidence: 99%

See 2 more Smart Citations

Maximum efficiency of the electro-osmotic pump

Miao

Wang

et al. 2011

Phys. Rev. E

Self Cite

View full text Add to dashboard Cite

show abstract

“…Such correlated variation also emphasizes the need for having both the ions and counterions be within the computational domain so that their interaction can be treated in a mathematically self-consistent manner. Fourth, the timevarying EO effect has been widely observed but rarely reported or addressed [73,74]. In particular, no theoretical study has been carried out to investigate whether there can be an intrinsic (noninertial) time dependence to the EO effect, even though from physical considerations the inevitable existence of diffusive counterion currents must give rise to a relaxation process.…”

Section: Introductionmentioning

confidence: 99%

Self-Consistent Approach to Global Charge Neutrality in Electrokinetics: A Surface Potential Trap Model

Wan

Liao

et al. 2014

Phys. Rev. X

Self Cite

View full text Add to dashboard Cite

In this work, we treat the Poisson-Nernst-Planck (PNP) equations as the basis for a consistent framework of the electrokinetic effects. The static limit of the PNP equations is shown to be the charge-conserving Poisson-Boltzmann (CCPB) equation, with guaranteed charge neutrality within the computational domain. We propose a surface potential trap model that attributes an energy cost to the interfacial charge dissociation. In conjunction with the CCPB, the surface potential trap can cause a surface-specific adsorbed charge layer σ. By defining a chemical potential μ that arises from the charge neutrality constraint, a reformulated CCPB can be reduced to the form of the Poisson-Boltzmann equation, whose prediction of the Debye screening layer profile is in excellent agreement with that of the Poisson-Boltzmann equation when the channel width is much larger than the Debye length. However, important differences emerge when the channel width is small, so the Debye screening layers from the opposite sides of the channel overlap with each other. In particular, the theory automatically yields a variation of σ that is generally known as the "charge regulation" behavior, attendant with predictions of force variation as a function of nanoscale separation between two charged surfaces that are in good agreement with the experiments, with no adjustable or additional parameters. We give a generalized definition of the ζ potential that reflects the strength of the electrokinetic effect; its variations with the concentration of surface-specific and surfacenonspecific salt ions are shown to be in good agreement with the experiments. To delineate the behavior of the electro-osmotic (EO) effect, the coupled PNP and Navier-Stokes equations are solved numerically under an applied electric field tangential to the fluid-solid interface. The EO effect is shown to exhibit an intrinsic time dependence that is noninertial in its origin. Under a step-function applied electric field, a pulse of fluid flow is followed by relaxation to a new ion distribution, owing to the diffusive counter current. We have numerically evaluated the Onsager coefficients associated with the EO effect, L 21 , and its reverse streaming potential effect, L 12 , and show that L 12 ¼ L 21 in accordance with the Onsager relation. We conclude by noting some of the challenges ahead.

show abstract

Maximizing fluid delivered by bubble‐free electroosmotic pump with optimum pulse voltage waveform

Tawfik

Díez

2016

Electrophoresis

View full text Add to dashboard Cite

In generating high electroosmotic (EO) flows for use in microfluidic pumps, a limiting factor is faradaic reactions that are more pronounced at high electric fields. These reactions lead to bubble generation at the electrodes and pump efficiency reduction. The onset of gas generation for high current density EO pumping depends on many parameters including applied voltage, working fluid, and pulse duration. The onset of gas generation can be delayed and optimized for maximum volume pumped in the minimum time possible. This has been achieved through the use of a novel numerical model that predicts the onset of gas generation during EO pumping using an optimized pulse voltage waveform. This method allows applying current densities higher than previously reported. Optimal pulse voltage waveforms are calculated based on the previous theories for different current densities and electrolyte molarity. The electroosmotic pump performance is investigated by experimentally measuring the fluid volume displaced and flow rate.

show abstract

Digital flow control of electroosmotic pump: Onsager coefficients and interfacial parameters determination

Cited by 13 publications

References 25 publications

Maximum efficiency of the electro-osmotic pump

Maximum efficiency of the electro-osmotic pump

Self-Consistent Approach to Global Charge Neutrality in Electrokinetics: A Surface Potential Trap Model

Maximizing fluid delivered by bubble‐free electroosmotic pump with optimum pulse voltage waveform

Contact Info

Product

Resources

About