Investigation of structural properties of electrosmotic flow in a nanochannel by molecular dynamics simulation

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Electro-osmotic flow of an aqueous electrolyte solution between two parallel silicon walls was studied by molecular dynamics simulation. Also, effects of the electrolyte solution on the electro-osmotic flow properties were examined by varying type of the dissolved salt. To achieve this goal, two mono-valent salts (NaCl & KCl), a divalent salt (MgCl2), and a trivalent salt (LaCl3) were simulated and the obtained results were compared together. The unique point of the present study is that all of the events happened in the flow properties are analyzed by investigating the changes made in the electrical double layer (EDL) properties. It was found that flow velocity rises from zero to a larger value in the EDL, and it remains constant in the bulk flow. Obtained profiles showed that the electro-osmotic flow formed by a mono-valent salt is stronger than the flow formed by divalent and trivalent salts. Also it was observed that the flow velocity suddenly decreases, immediately after the EDL's boundaries. Results showed that by increasing the valence of the salt, the number of cations attracted in the stern layer increases and so the ability of the EDL to form the electro-osmotic flow decreases. In addition, it was observed that physical properties of the driving ions (which are the cations in this work) like the ionic diameter; affect on the electro-osmotic flow properties.

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Journal of Solid and Fluid Mechanics
Volume 2, Issue 4 - Serial Number 4
January and February 2013
Pages 77-91

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