| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 97 === In this work, we present an experimental and numerical investigation on the concentration polarization in hybrid micro/nanochannels. Two issues were investigated: (1) pH value effect on the occurrence of concentration polarization and the I-V curve (i.e. S curve) and (2) nonlinear electrokinetic flow at the interface between micro/nanochannels.
In the first part of this thesis, we explore the voltage required to impose, in different concentration of electrolyte and surface charge density, so that the concentration polarization within channel occured. Results show that the low concentration of the electrolyte and high surface charge density will occur concentration polarization under low voltage. In addition, the experimental results showed that the applied voltage required to produce the concentration polarization decreases with increasing the pH value of the electrolyte.
The second part of this thesis focuses on the flow near the interface of micro/nanochannel. We utilized electrical measurements and evaluated the electrical conductivity and the electrical field within the depletion region. Fluorescent particles are injected into the channel to observe flow field near nano/microchannel interface. Results show that the electrical conductivity were decreased and the electrical field were increased in depletion region and fast fluid vortices were generated at the anodic side of the nanochannel due to the nonequilibrium electroosmotic flow.
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