Patterning nanodomains with orthogonal functionalities: Solventless synthesis of self-sorting surfaces

A simple method to fabricate a multifunctional patterned platform on the nanometer scale is demonstrated. The platform contains two reactive functional groups on the surface: one is an acetylene group which can be functionalized via click chemistry, and the other is an amine group which can also be functionalized by classic carbodiimide chemistry with N-hydroxysuccinimide (NHS). The click-active and amine surface could be obtained from polymer coating of poly(propargyl methacrylate) (PPMA) via initiated chemical vapor deposition (iCVD) and poly(allylamine) (PAAm) via a plasma polymerization process, respectively, utilizing commercially available monomers. A capillary force lithography (CFL) process was applied on a stacked film of a PPMA layer on PAAm, and CFL could selectively pattern PPMA maintaining the bottom PAAm layer intact, which completes the multifunctional nanopatterns. The minimum feature size of this nanopattern was 110 nm. The entire fabrication process is solventless and low temperature, which can minimize the loss of functionalities. The click and NHS reactions are highly orthogonal to each other so that nonspecific immobilization can be minimized. These advantageous characteristics enable the covalent functionalization of two independent components in a one-pot functionalization process in self-recognized way. The one-pot orthogonal functionalization was performed in an aqueous solution at room temperature, which is biocompatible. Considering the versatility and generality of the reactions used here, we believe this platform can be easily extended to various biodevice applications.