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Resolving Anomalies in Predicting Electrokinetic Energy Conversion Efficiencies of Nanofluidic Devices.

Majumder S, Dhar J, Chakraborty S - Sci Rep (2015)

Bottom Line: We devise a new approach for capturing complex interfacial interactions over reduced length scales, towards predicting electrokinetic energy conversion efficiencies of nanofluidic devices.By embedding several aspects of intermolecular interactions in continuum based formalism, we show that our simple theory becomes capable of representing complex interconnections between electro-mechanics and hydrodynamics over reduced length scales.The present model, thus, may be employed to rationalize the discrepancies between low energy conversion efficiencies of nanofluidic channels that have been realized from experiments, and the impractically high energy conversion efficiencies that have been routinely predicted by the existing theories.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Indian Institute of Technology Kharagpur Kharagpur 721302, INDIA.

ABSTRACT
We devise a new approach for capturing complex interfacial interactions over reduced length scales, towards predicting electrokinetic energy conversion efficiencies of nanofluidic devices. By embedding several aspects of intermolecular interactions in continuum based formalism, we show that our simple theory becomes capable of representing complex interconnections between electro-mechanics and hydrodynamics over reduced length scales. The predictions from our model are supported by reported experimental data, and are in excellent quantitative agreement with molecular dynamics simulations. The present model, thus, may be employed to rationalize the discrepancies between low energy conversion efficiencies of nanofluidic channels that have been realized from experiments, and the impractically high energy conversion efficiencies that have been routinely predicted by the existing theories.

No MeSH data available.


Influence of the inclusion of various effects on the conversion efficiency η<inset> dimensionless streaming potential ratio  for a representative case of a hydrophilic surface, as a function of the dimensionless wall potential,.Various line numbers represent: 1) streaming potential estimation based on the classical PB model with no further effects being considered26, with  and ; 2) inclusion of the effects of the viscous sublayer with ys = 0.3 nm and ; 3) considering the effect of the permittivity sublayer with ydds = 0.10 nm; 4) inclusion of the effect of steric interactions v = 10−2; and 5) finally depicting the scenario with all four effects by adding the non-electrostatic interactions with α = −1.5. Credited authors: S. Majumder, J. Dhar and S. Chakraborty.
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f3: Influence of the inclusion of various effects on the conversion efficiency η<inset> dimensionless streaming potential ratio for a representative case of a hydrophilic surface, as a function of the dimensionless wall potential,.Various line numbers represent: 1) streaming potential estimation based on the classical PB model with no further effects being considered26, with and ; 2) inclusion of the effects of the viscous sublayer with ys = 0.3 nm and ; 3) considering the effect of the permittivity sublayer with ydds = 0.10 nm; 4) inclusion of the effect of steric interactions v = 10−2; and 5) finally depicting the scenario with all four effects by adding the non-electrostatic interactions with α = −1.5. Credited authors: S. Majumder, J. Dhar and S. Chakraborty.

Mentions: Fig. 2a depicts the effects of addition of the four factors as mentioned earlier onto the classical Poisson-Boltzmann equation at moderately high electrolyte concentrations . To depict the case of a higher concentration regime, the dimensionless Debye length is considered as , with the corresponding steric factor v = 0.01 signifying a strong steric interaction among the ions, especially at high wall potential. A hydrophobic surface is considered for this representative scenario. Here it can be clearly seen that the addition of each effect shows a distinctive change in the prediction of the streaming potential behavior with increasing wall potential. The effect of steric interactions becomes prominent for high values of wall potential, where the crowding of counterions tends to be large and the concept of ionic concentration saturation becomes significant. Comparing with Fig. 3, it is clear that in different concentration regimes, the four effects produce distinctive implications and neither of these effects can be neglected in order to make a prediction across varying system conditions. Fig. 2b further shows the enhanced effect of the steric factor, at higher steric interaction zones, for a particular value of . Increase in steric factor increases the streaming potential due to repulsion of the ionic charge distribution towards the bulk, thereby increasing the streaming current. As discussed above, the increase is more prominent for high wall potential as well. We now proceed to discuss how these effects comparatively affect the resultant streaming field in case of a low concentrated electrolyte.


Resolving Anomalies in Predicting Electrokinetic Energy Conversion Efficiencies of Nanofluidic Devices.

Majumder S, Dhar J, Chakraborty S - Sci Rep (2015)

Influence of the inclusion of various effects on the conversion efficiency η<inset> dimensionless streaming potential ratio  for a representative case of a hydrophilic surface, as a function of the dimensionless wall potential,.Various line numbers represent: 1) streaming potential estimation based on the classical PB model with no further effects being considered26, with  and ; 2) inclusion of the effects of the viscous sublayer with ys = 0.3 nm and ; 3) considering the effect of the permittivity sublayer with ydds = 0.10 nm; 4) inclusion of the effect of steric interactions v = 10−2; and 5) finally depicting the scenario with all four effects by adding the non-electrostatic interactions with α = −1.5. Credited authors: S. Majumder, J. Dhar and S. Chakraborty.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4593964&req=5

f3: Influence of the inclusion of various effects on the conversion efficiency η<inset> dimensionless streaming potential ratio for a representative case of a hydrophilic surface, as a function of the dimensionless wall potential,.Various line numbers represent: 1) streaming potential estimation based on the classical PB model with no further effects being considered26, with and ; 2) inclusion of the effects of the viscous sublayer with ys = 0.3 nm and ; 3) considering the effect of the permittivity sublayer with ydds = 0.10 nm; 4) inclusion of the effect of steric interactions v = 10−2; and 5) finally depicting the scenario with all four effects by adding the non-electrostatic interactions with α = −1.5. Credited authors: S. Majumder, J. Dhar and S. Chakraborty.
Mentions: Fig. 2a depicts the effects of addition of the four factors as mentioned earlier onto the classical Poisson-Boltzmann equation at moderately high electrolyte concentrations . To depict the case of a higher concentration regime, the dimensionless Debye length is considered as , with the corresponding steric factor v = 0.01 signifying a strong steric interaction among the ions, especially at high wall potential. A hydrophobic surface is considered for this representative scenario. Here it can be clearly seen that the addition of each effect shows a distinctive change in the prediction of the streaming potential behavior with increasing wall potential. The effect of steric interactions becomes prominent for high values of wall potential, where the crowding of counterions tends to be large and the concept of ionic concentration saturation becomes significant. Comparing with Fig. 3, it is clear that in different concentration regimes, the four effects produce distinctive implications and neither of these effects can be neglected in order to make a prediction across varying system conditions. Fig. 2b further shows the enhanced effect of the steric factor, at higher steric interaction zones, for a particular value of . Increase in steric factor increases the streaming potential due to repulsion of the ionic charge distribution towards the bulk, thereby increasing the streaming current. As discussed above, the increase is more prominent for high wall potential as well. We now proceed to discuss how these effects comparatively affect the resultant streaming field in case of a low concentrated electrolyte.

Bottom Line: We devise a new approach for capturing complex interfacial interactions over reduced length scales, towards predicting electrokinetic energy conversion efficiencies of nanofluidic devices.By embedding several aspects of intermolecular interactions in continuum based formalism, we show that our simple theory becomes capable of representing complex interconnections between electro-mechanics and hydrodynamics over reduced length scales.The present model, thus, may be employed to rationalize the discrepancies between low energy conversion efficiencies of nanofluidic channels that have been realized from experiments, and the impractically high energy conversion efficiencies that have been routinely predicted by the existing theories.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Indian Institute of Technology Kharagpur Kharagpur 721302, INDIA.

ABSTRACT
We devise a new approach for capturing complex interfacial interactions over reduced length scales, towards predicting electrokinetic energy conversion efficiencies of nanofluidic devices. By embedding several aspects of intermolecular interactions in continuum based formalism, we show that our simple theory becomes capable of representing complex interconnections between electro-mechanics and hydrodynamics over reduced length scales. The predictions from our model are supported by reported experimental data, and are in excellent quantitative agreement with molecular dynamics simulations. The present model, thus, may be employed to rationalize the discrepancies between low energy conversion efficiencies of nanofluidic channels that have been realized from experiments, and the impractically high energy conversion efficiencies that have been routinely predicted by the existing theories.

No MeSH data available.