Liquid crystal alignment on replicated nanostructured surfaces

Interaction of liquid crystals with nanostructured surfaces is studied experimentally. Whereas photolithographic or AFM methods were used in the past for surface structuring, we use besides photo lithography essentially replication methods for the creation of well-controlled nano-topologies. We established a laboratory process to prepare surface structures that can be as large as 4 x 4 inch and allow preparing test cells in a production like environment. We combined different methods and tested for soft embossing and direct writing in photoresist. Soft embossing was made with UV curable materials. The direct writing in photoresist was done by means of laser beam interferometry. Structure parameters were changed and the surfaces were characterized by surface anchoring energy measurements and by electro-optical switching behaviour. The obtained alignment is quite uniform over large surface areas despite of a certain variation of the surface parameters. In the case of interferemetrically produced grating structures with periods ranging from 350-800 nm strong anchoring was observed and no pretilt could be found.