Functional photoresists for sub-diffraction stimulated emission depletion lithography

Two novel photoresists were developed for the fabrication of sub-diffractionally sized polymeric nanostructures with chemically reactive surfaces. Using multiphoton polymerization as well as stimulated emission depletion (STED) lithography, chemically functional monomers were copolymerized with highly crosslinking triacrylate monomers to yield stable nanostructures. The polymer structure was thereby supplemented with chemical functionalities for further covalent modification reactions. The reactivity of mercapto- and carboxylate groups on the surface of the nanostructures was proved by orthogonally labeling them with reactive fluorophores. The photoresists can be used for stimulated emission depletion lithography and lateral line widths down to 55 nm were achieved. A threedimensional structure is shown that is made up with three compounds: a frame out of a unfunctionalized acrylate photoresist, and two intermediate networks made up with thiol- and carboxyl functional photoresists.