Modification of supported lipid membranes by atomic force microscopy

The atomic force microscope (AFM) was used to structurally modify supported lipid bilayers in a controlled quantitative manner. By increasing the force applied by the AFM tip, lipid was removed from the scanned area, leaving a cut through the lipid bilayer. Cuts were repaired with the AFM by scanning the region with a controlled force and driving lipid back into the cut. A slow self-annealing of cuts was also observed

Evidence of pronounced positional order at the graphite-liquid crystal interface of a bulk nematic material

We present scanning tunneling microscopy images of a bulk nematic liquid crystal, viz., 4'-n-hexyl-4-cyanobiphenyl, on the surface of graphite. These images clearly show the existence of pronounced positional order at the solid-liquid crystal interface for a material with no positional order in the bulk. A feature of the molecular arrangement is the pronounced interdigitation of the aromatic cores. The unit cell consists of two opposing molecules, the aromatic core of one of them lying flat on the graphite surface, while the core of the adjacent molecule lies on its side. The packing arrangement also features large open spaces of uncovered substrate between the alkyl tails. The molecular arrangement is compared with that of the smectic alkylcyanobiphenyls