| Colloidal suspensions are complex fluids that consist of mesoscopic particles suspended in a solvent, e.g. water, oil, etc. In this thesis, the objective is to investigate the four aspects of colloidal suspensions: electrorotation, dielectrophoresis, dielectric dispersion spectrum, and nonlinear alternating current (AC) response.; The traditional theories failed to fit the recent experimental data, and hence, for the purpose of a better fitting, we aim to develop new theories. In addition, our theories also predicted some new phenomena which are expected to be verified in experiments.; Electrorotation has been increasingly employed as a sensitive tool for non-invasive studies of a broad variety of microparticles, ranging from living cells to spores and seeds, as well as synthetic materials. In order to analyze the abundant experimental data, we extend here the existing theory by taking into account crucial elements, such as inhomogeneities, multipolar interactions, nonspherical shapes as well as many-body (local-field) effects. Good agreement is shown between our theoretical results and the experimental data.; Dielectrophoresis is typically used for micromanipulation and separation of biological cellular size particles, and it has recently been successfully applied to submicron size particles as well. Specific applications include diverse problems in medicine, colloidal science and nanotechnology. To analyze the recent experimental observations, we present a theory which includes the effects of both charging and multipolar interactions. Our theoretical results are favorably compared with the recent experimental observations.; Recent experiments revealed that the dielectric dispersion spectrum of fission yeast cells in a suspension was mainly composed of two sub-dispersions. The low-frequency sub-dispersion depended on the cell length, while the high-frequency one was independent of it. However, the existing theory does not fit the experimental data. Hence, we here put forth a theory which does fit, by considering the effects of membranes and/or dipole rotations.; Electrorheological fluids which are subjected to an intense electric field can result in field-induced anisotropic structures. The rapid field-induced aggregation and the large anisotropy in their properties render this field-structured material potentially important for technological applications. (Abstract shortened by UMI.)... |
