Automated Local Polymer Writing into a Mesoporous Silica Thin Film Using a Commercially Available Fluorescence Microscope and Oxygen Tolerant PET-RAFT

Functionalization of mesoporous material with polymers to modify its attributes e.g. ion transport or wettability is a much-studied field. A localized functionalization can then be used for e.g. lab-on-a-chip devices with hydrophobic barriers and hydrophilic reaction chambers or janus membrane-like structures for fluid-based material separation. One way to produce locally confined polymer functionalization is to use light-induced polymerization in combination with local illumination. The use of photomasks allows for locally restricted illumination and is well suited for mass production but lacks flexibility when developing new patterns. A direct “writing” of polymer with a precisely controlled local illumination is needed for rapid prototyping in research and development. While the use of UV-induced polymerization is well-known, the development of visible light-induced methods made the usage of commercially available fluorescence microscopes with laser illumination for polymer writing possible. A key step to make this approach more feasible was the development of an oxygen tolerant polymerization, making special equipment for the control of reaction conditions, like a glove-box, unnecessary.<br/>Here, we present an oxygen tolerant photoinduced electron/energy transfer reversible addition–fragmentation chain transfer polymerization (PET-RAFT) in combination with a commercially available fluorescence microscope (Nikon Ti2-E) for automated precise and flexible micrometer-scale polymer writing into mesoporous silica thin films. Optimization of illumination time and power was performed resulting in the ability to “write” any given monochromatic pixel image with a chosen polymer into the mesoporous silica film within a reasonable time frame. Three monomers with varying attributes were tested with the system (DMAEMA, MEP, METAC). A consecutive polymerization of all three monomers in close proximity as well as a re-initiation of polymerization with a different monomer at the same spot for the functionalization with block-copolymers was successfully performed.