Susanne Klein

We are in the middle of another revolution in information processing and distribution. After the invention of script and then print, pictures are taking over again. The number of gadgets with displays is larger than the world population. On average, every single person on earth owns at least one device with a display on it. These displays are the portals to everything we do: communicating, reading, shopping, learning, etc. But are they up to the job? The most successful display technology to date is still the liquid crystal display. It is a well-established technology that can be scaled in size from small to large and, depending on the drive electronics, has no significant inherent limits to resolution. However, poor light efficiency and data congestion caused by high pixel densities are still technical challenges in need of good solutions. Could electrophoresis in a liquid crystal host be the answer? The fundamental basics and technical challenges of this interesting new approach will be discussed.

In recent years, several papers reported an enhanced dielectric anisotropy when ferroelectric particles were suspended in a liquid crystal. These results seem to be sensitive to the liquid crystal used and the preparation method of the ferroelectric particles. In this paper, we compare different preparation methods of suspended barium titanate in two different liquid crystal hosts. As a control experiment, we followed similar preparation steps with non-ferroelectric silica particles. In all cases, we found a broadening of the optical Frederiks transition but no change in the dielectric anisotropy. Raman spectroscopy has been used to investigate the loss of tetragonal structure in the barium titanate as a function of milling time and particle size. As reported in the earlier literature, barium titanate does not exhibit a well-defined tetragonal crystal structure below a certain particle size and loses its ferroelectric features. This provides a simple rationalization for the absence of any dielectric enhancement.