| Summary: | 碩士 === 國立臺灣大學 === 高分子科學與工程學研究所 === 105 === Considering recent applications of diffusiophoresis in biosensing technology, we model the diffusiophoresis of a zwitterionic, pH-regulated polyelectrolyte (PE) in a solution containing multiple ionic species. In particular, the influences of particle shape and charged boundary are discussed. In the former, we extend previous analysis for the diffusiophoresis of a toroidal PE at a fixed charge density to the case of pH-regulated condition. The diffusiophoretic behaviors of the toroidal PE considered under various conditions are examined by varying its functional group density, size, and softness, and the solution pH and bulk salt concentration. We show that the diffusiophoretic behavior and the effective charge density of a toroidal PE can be different both quantitatively and qualitatively from the corresponding spherical PE. In the latter, we simulate the diffusiophoretic behaviors of a spherical PE in a silicon dioxide nanochannel by varying the solution pH, the bulk salt concentration, and the nanochannel radius. In this case, the interaction of the double layer of the PE and that of the nanochannel influences significantly the electric, the flow, and the ionic concentration fields near the PE, yielding profound diffusiophoretic behaviors. We show that both the magnitude and the direction of diffusiophoretic velocity depend highly on the conditions assumed in these two chapters, implying that an efficient separation process can be designed.
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