| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 99 === The ionic transport characteristics through nanochannels are examined numerically in this study. The coupled Navier-Stokes equation for the fluid flow, Poisson equation for the electric potential distribution, and the extended Nernst-Planck equation for the species transport are solved. This study particularly focus on the relationship between the current passing through the nanochannel and the externally applied voltage (I-V curve), including the Ohmic current, limiting current, and over-limiting current regimes.
The study first aims to clarify the effect of the microchannel or reservoirs that connected at the ends of the nannochannel on the I-V curve. Based on the results reported in this study, it was found that when the microchannel size is large, the I-V curves have no significant difference from the case with nanochannel connected with reservoirs. Secondly, this study examines the effect of the overall size of the nanochannel-microchannel junction on the I-V curve under the same nanochannel surface charge density and non-dimensional applied voltage. It was found that there was no significant difference in I-V curves in the Ohmic current regime for the three nanochannel-microchannel junction size studied. However, the I-V curve depends on the nanochannel-microchannel junction size in the limiting current, and over-limiting current regimes.
With the surface charge density varied along the nanochannel wall, the current rectification through the nanochannel was examined. It was found that the ionic current rectification depends greatly on the electrolyte bulk concentrations and the applied externally voltages. With low bulk electrolyte concentration and applied voltage in the over-limiting current regime, significant ionic current rectification can be found.
|
|---|
