Post-Fabrication Placement of Arbitrary Chemical Functionality on Microphase-Separated Thin Films of Amine-Reactive Block Copolymers

We report an approach to the post-fabrication placement of chemical functionality on microphase-separated thin films of a reactive block copolymer. Our approach makes use of an azlactone-containing block copolymer that microphase separates into domains of perpendicularly-oriented lamellae. These thin films present nanoscale patterns of amine-reactive groups (reactive stripes) that serve as handles for the immobilization of primary amine-containing functionality. We demonstrate that arbitrary chemical functionality can be installed by treatment with aqueous solutions under mild conditions that do not perturb underlying microphase-separated patterns dictated by the structure of the reactive block copolymer. This post-fabrication approach provides a basis for the development of modular approaches to the design of microphase-separated block copolymer thin films and access to coatings with patterned chemical domains and surface properties that would be difficult to prepare by the self-assembly and processing of functionally complex block copolymers

Photolithographic Synthesis of High-Density DNA and RNA Arrays on Flexible, Transparent, and Easily Subdivided Plastic Substrates

The photolithographic fabrication of high-density DNA and RNA arrays on flexible and transparent plastic substrates is reported. The substrates are thin sheets of poly­(ethylene terephthalate) (PET) coated with cross-linked polymer multilayers that present hydroxyl groups suitable for conventional phosphoramidite-based nucleic acid synthesis. We demonstrate that by modifying array synthesis procedures to accommodate the physical and chemical properties of these materials, it is possible to synthesize plastic-backed oligonucleotide arrays with feature sizes as small as 14 μm × 14 μm and feature densities in excess of 125 000/cm², similar to specifications attainable using rigid substrates such as glass or glassy carbon. These plastic-backed arrays are tolerant to a wide range of hybridization temperatures, and improved synthetic procedures are described that enable the fabrication of arrays with sequences up to 50 nucleotides in length. These arrays hybridize with S/N ratios comparable to those fabricated on otherwise identical arrays prepared on glass or glassy carbon. This platform supports the enzymatic synthesis of RNA arrays and proof-of-concept experiments are presented showing that the arrays can be readily subdivided into smaller arrays (or “millichips”) using common laboratory-scale laser cutting tools. These results expand the utility of oligonucleotide arrays fabricated on plastic substrates and open the door to new applications for these important bioanalytical tools