Versatile Surface Functionalization and Micropatterning Enabled By Microcontact Printing of Poly-4-Aminostyrene

Microcontact printing (μCP) of polyelectrolytes is a facile and powerful method for surface micropatterning and functionalization. Poly-4-aminostyrene (PAS) is a polyelectrolyte that can be converted to aryldiazonium salt and has a pH-dependent hydrophobicity. Here we report μCP of PAS and extension of this technique for a number of applications. First, the microcontact-printed PAS can be diazotized to immobilize DNA and avidin. Moreover, the diazotization process does not interfere with functionality of avidin. Second, this method allows micropatterning single-walled carbon nanotubes and gold nanoparticles. Third, the diazotized PAS can be used to enable μCP of a gold crossbar structure on graphite surface. Fourth, the hydrophobic property of PAS at the neutral pH allows the microcontact-printed PAS-based multilayer as masks for wet etching of gold. Finally, PAS-based multilayer and sputter-coated gold can be microcontact-printed to produce polyelectrolyte-metal hybrid microparticles that can be further functionalized with protein by diazotizing the PAS. This technique significantly expands the capability of μCP for several applications including micropatterning biomolecules and nanomaterials, printing gold microstructures on carbon, preparing masks for wet etching of gold, and producing highly engineered microparticles.