PHOTOPATTTOCELL · Photopatterning of Cellulose Films for Creation of 2- and 3-Dimensional Nanostructures

While photolithographic techniques are well established for patterning of semiconductors, they have not been employed for polysaccharide based materials to a large extent. The main idea of this project is to generate nano-patterned cellulose thin films using ideas and concepts from semiconductor industry to create 2 and 3 dimensionally structured cellulose surfaces. As starting material for the generation of cellulose surfaces, trimethylsilyl cellulose (TMSC) containing (2-photon sensitive) photoacid generators (PAG) is used which is deposited on different kinds of surfaces by spin coating. The use of mask aligners and UV-light or 2-photon absorption lithography converts exposed areas to cellulose (silyl groups are cleaved off by the generated acid) while in the unexposed areas TMSC remains. After the patterning step, TMSC can be selectively dissolved using an appropriate solvent or, alternatively, the converted cellulose can be digested using cellulases. Using the latter route remaining TMSC can be converted to cellulose in an additional step. As a result, 2 and 3 dimensionally nanostructured films can be obtained which have a large potential as material for semiconductor industry, in medicine (for growth of stem cells, antifouling materials) and in optical materials (refractive index changes). While the main focus of the project is to generate nano-structured cellulose films, this approach can be easily extended to other polysaccharides as well. The whole project aims at reducing organic solvents and to use mainly so-called eco-solvents.