Real space and Fourier microscopy of colloidal suspensions confined to a parallel plate geometry

Optical microscopy is known as a versatile tool to investigate the structure and dynamics of ordered colloidal suspensions. We present a version facilitating the quasisimultaneous access to global structure information's via Fourier microscopy and local real-space analysis on the level of individual particles. For the latter the sampling volume was significantly enhanced in z direction manipulating the cover glass correction. The resulting image is a projection of x-y particle positions at different z into a two-dimensional plane of which two-dimensional projection correlation diagrams (PCDs) and radial averages were obtained. For crystals and layered structures the PCDs contain valuable information on in-plane order and the relative position of neighboring planes. Time resolved measurements give access to statistically significant average particle (layer) trajectories, which in principle are directly comparable to simulation results. The instrument is tested on a variety of ordered colloidal structures under equilibrium conditions and under linear shear in a plate-plate optical cell. (C) 2004 American Institute of Physics.