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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.


Schematic representation of the pressure driven flow of an electrolytic medium through a nanofluidic substrate.Near-wall regimes of altered viscosity and permittivity, as compared to the bulk, are schematically depicted. For illustration, the substrate is assumed to be negatively charged, so that there are abundant positive ions (counterions; shown by green colour) as compared to negative ions (coions; shown by red colour). Balance of streaming current and conduction current, in presence of the preferential distribution of counterions in the EDL as compared to coions, establishes a streaming potential. This enables the conversion of hydraulic energy to electrical energy, when the setup is connected to an external resistor. The maximum possible electrical power output through the external resistor (denoted by Powermax) is proportional to the product of the streaming field potential Es and streaming current Is (detailed in the following sections). Credited authors: S. Majumder, J. Dhar and S. Chakraborty.
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f1: Schematic representation of the pressure driven flow of an electrolytic medium through a nanofluidic substrate.Near-wall regimes of altered viscosity and permittivity, as compared to the bulk, are schematically depicted. For illustration, the substrate is assumed to be negatively charged, so that there are abundant positive ions (counterions; shown by green colour) as compared to negative ions (coions; shown by red colour). Balance of streaming current and conduction current, in presence of the preferential distribution of counterions in the EDL as compared to coions, establishes a streaming potential. This enables the conversion of hydraulic energy to electrical energy, when the setup is connected to an external resistor. The maximum possible electrical power output through the external resistor (denoted by Powermax) is proportional to the product of the streaming field potential Es and streaming current Is (detailed in the following sections). Credited authors: S. Majumder, J. Dhar and S. Chakraborty.

Mentions: Electrokinetics in nanofluidic channels is considered to be an emerging mechanism for converting hydraulic form of energy to electrical form1011121314151617. An electrically neutral fluid in contact with solid substrates often develops surface charges that are counterbalanced by excess charges of opposite sign distributed in an interfacial charged layer (also known as electrical double layer; EDL)1118192021. Excess counterions within the mobile part of the EDL may be forced by an externally applied pressure gradient to preferentially migrate downstream towards the end of the nanochannel, thereby developing an electrical potential difference across the channel in a dynamic environment (known as streaming potential)222324. The resultant current, if diverted through an external resistor, may convert the supplied hydraulic form of energy to electrical form (please see the schematic in Fig. 1 for a pictorial representation of the physical scenario)10112526. Theoretically, researchers have postulated that dramatic augmentations in the concerning energy conversion efficiency may be plausible by exploiting special features of nanofluidic devices, such as interfacial slip2728293031. However, in reality, experimentally obtained energy conversion efficiencies in nanofluidic channels have been observed to be significantly lower, as compared to those predicted by these theoretical simulations732.


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

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

Schematic representation of the pressure driven flow of an electrolytic medium through a nanofluidic substrate.Near-wall regimes of altered viscosity and permittivity, as compared to the bulk, are schematically depicted. For illustration, the substrate is assumed to be negatively charged, so that there are abundant positive ions (counterions; shown by green colour) as compared to negative ions (coions; shown by red colour). Balance of streaming current and conduction current, in presence of the preferential distribution of counterions in the EDL as compared to coions, establishes a streaming potential. This enables the conversion of hydraulic energy to electrical energy, when the setup is connected to an external resistor. The maximum possible electrical power output through the external resistor (denoted by Powermax) is proportional to the product of the streaming field potential Es and streaming current Is (detailed in the following sections). 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

f1: Schematic representation of the pressure driven flow of an electrolytic medium through a nanofluidic substrate.Near-wall regimes of altered viscosity and permittivity, as compared to the bulk, are schematically depicted. For illustration, the substrate is assumed to be negatively charged, so that there are abundant positive ions (counterions; shown by green colour) as compared to negative ions (coions; shown by red colour). Balance of streaming current and conduction current, in presence of the preferential distribution of counterions in the EDL as compared to coions, establishes a streaming potential. This enables the conversion of hydraulic energy to electrical energy, when the setup is connected to an external resistor. The maximum possible electrical power output through the external resistor (denoted by Powermax) is proportional to the product of the streaming field potential Es and streaming current Is (detailed in the following sections). Credited authors: S. Majumder, J. Dhar and S. Chakraborty.
Mentions: Electrokinetics in nanofluidic channels is considered to be an emerging mechanism for converting hydraulic form of energy to electrical form1011121314151617. An electrically neutral fluid in contact with solid substrates often develops surface charges that are counterbalanced by excess charges of opposite sign distributed in an interfacial charged layer (also known as electrical double layer; EDL)1118192021. Excess counterions within the mobile part of the EDL may be forced by an externally applied pressure gradient to preferentially migrate downstream towards the end of the nanochannel, thereby developing an electrical potential difference across the channel in a dynamic environment (known as streaming potential)222324. The resultant current, if diverted through an external resistor, may convert the supplied hydraulic form of energy to electrical form (please see the schematic in Fig. 1 for a pictorial representation of the physical scenario)10112526. Theoretically, researchers have postulated that dramatic augmentations in the concerning energy conversion efficiency may be plausible by exploiting special features of nanofluidic devices, such as interfacial slip2728293031. However, in reality, experimentally obtained energy conversion efficiencies in nanofluidic channels have been observed to be significantly lower, as compared to those predicted by these theoretical simulations732.

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.