Electrically controlled defects at a liquid crystal-polyimide interface

We report results on the effect of introducing a small quantity of oligomer particles inside a liquid crystal (LC) display. We observe a dramatic change in the properties of the LC-substrate interface. Upon applying an electric field, a pi-wall defect network appears that is stable in the absence of further electric perturbation but can be erased by a suitable pulse in a well-defined range of temperature and frequency. The appearance of the defects and their dimensions depend on the cell age, i.e. on the time required by the guest to deposit on the surface. Hypotheses on the phenomenon are reported.