| This thesis describes advances in understanding fluid microstructure by developing techniques to produce and interpret images by cryo-electron and optical microscopy. The Controlled Environment Vitrification System (CEVS) permits preparation of hydrated biological and colloidal samples for cryo-electron microscopy from a temperature- and saturation-controlled environment, thereby preventing artifacts of conventional preparation techniques. An image of such a specimen is the projection of its distributed atomic potential and mass density onto a viewing plane, distorted by the effects of aberrations and defocus. Images of micelles, swollen micelles, vesicles and liposomes have been modeled by accounting for these distortions; they indicate that cylindrical micelles can be distinguished from a chain of micellar beads and that spherical micelles as small as 4 nm can be resolved, and so can bilayers spaced as close as 3 nm. A polarized microscope image is the projection of the polarizer- and analyzer-direction component of the local electric susceptibility tensor within the specimen onto an image plane. Images computed from this theory range from the well-known Maltese crosses to more intricate patterns from nematic, smectic, and cholesteric liquid crystals. Cryo-microscopy produces negatives with wide contrast range. Two techniques of unsharp masking have been developed to reduce contrast without losing detail, thereby yielding significantly better and reproducible prints than the conventional method of dodging and burning.;Images of vesicles, liquid crystals, micelles, swollen micelles and microemulsions, are displayed and related to their microstructure. The images show structures never postulated before: watery and floppy vesicles, undulating tubes, and widely spaced bilayers, indicating that thermal fluctuations may cause unbinding disruptions of the lamellar structure of liposomes. Mixtures of a surfactant with a detergent show several structures that form as vesicles are transformed into spherical micelles: they include vesicles with broken walls, bilayer fragments and disk-like micelles. Physically associated amphiphilic structures remain unperturbed during sample preparation: this is demonstrated because spherical micelles, the most labile of all amphiphilic systems, can be visualized. Images from microemulsions show, for the first time, a rather abrupt transition from discontinuous oil-in-water to bicontinuous microstructure. |
