One-dimensional axial simulation of electric double layer overlap effects in devices combining micro- and nanochannels |
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Authors: | Brice T Hughes Jordan M Berg Darryl L James Akif Ibraguimov Shaorong Liu Henryk Temkin |
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Affiliation: | (1) Mechanical Engineering Department and Nano Tech Center, Texas Tech University, Lubbock, TX 79409, USA;(2) Department of Mathematics and Statistics, Texas Tech University, Lubbock, TX 79409, USA;(3) Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, USA;(4) Electrical Engineering Department and Nano Tech Center, Texas Tech University, Lubbock, TX 79409, USA |
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Abstract: | This paper presents a numerical steady-state model of ion transport in micro- and nanofluidic devices with widely varying
geometric scale, such as transitions between micro- and nanochannels. Finite element or finite volume simulation of such problems
is challenging, due to the number of elements needed to produce a satisfactory mesh. Here, only the lengthwise channel dimension
is meshed; standard analytical approximations are used to incorporate cross-channel properties. Singularly perturbed cases
are built up by continuation. The method is shown to reproduce our previously reported measurements of electric double-layer
effects on conductivity, ion concentration, and ion enhancement and depletion. Comparison with 2-D simulations reported in
the literature shows that effects on accuracy due to the 1-D approximation are small. The model incorporates analytical models
of surface charge density taken from the literature. This enables predictive simulation with reasonable accuracy using published
parameter values, or these values may be tuned based on experiment to give improved results. Use of the model for iterative
design and parameter estimation is demonstrated. |
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Keywords: | Ion transport Electrokinetic flow Scale transition Electric double layer overlap Singular perturbation Numerical modeling Continuation methods Poisson-Nernst-Planck equations |
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