Scanning Probe Lithography for bioactive Functionalization

This thesis deals with the diverse field of Scanning probe lithography (SPL), which offer a wide range of functionalization options for bioactive surfaces, device, and sensor functionalization. The mild process parameters in dip-pen nanolithography (DPN) and polymer pen lithography (PPL) as well as microchannel cantilever spotting (µCS) enable direct write approaches for many otherwise not easy to pattern substances as easily decomposing chemicals or bioactive enzymes and proteins. One of the key applications developed during the course of the research was the multi-color patterning by PPL for the generation of sub-cellular scaled multi-component patterns over surface areas in the square centimeter range. To achieve a virtually unlimited library of orthogonal binding tags, the technique was used to print oligo-nucleotide for subsequent DDI of fluorophores and proteins on the arrays. The SPL generated patterns allowed new insights on the events in the “immunological synapse” of mast cells during allergen recognition and the modulation of the involved receptor’s fates during introduction of glucocorticosteroids. Another application is the capture of rare cells out of bodily fluids e.g. for quantification CTCs. In all cell work, encapsulation of the bioactive arrays by microfluidics lead to easier handling and use, and more reliable and reproducible incubation procedures. Furthermore, we introduced advancements that allow the traditionally 2D functionalization SPL methods to target much more complex devices. This allows e.g. the site-specific and multiplexed functionalization of highly sensitive WGM sensor structures by DPN and PPL for sensing applications in highly complex media as e.g. serum. Similarly, complex photonic circuitry or sophisticated graphene devices can be fabricated in high quality by conventional photolithography and EBL and subsequently be functionalized by the newly developed methods. Graphene as substrate for L-DPN shows a number of interesting phenomena, e.g. quenching of fluorescence, electronic coupling and self-limited spreading of the lipid membranes. These properties might be exploited to build especially sensitive and specific sensor devices based on charge transfer and shielding. The borders between different lithographic methods will likely blur further in the future and integrative approaches – either subsequent rounds of different lithography types, or combinations of different lithographic principles in one step – will play a much bigger role.