Self-assembly of functionalized spherical nanoparticles on chemically patterned microstructures

The production of hierarchical nanopatterns (using a top-down microfabrication approach combined with a subsequent bottom-up self-assembly process) will be an important tool in many research areas. We report the fabrication of silica nanoparticle arrays on lithographically pre-patterned substrates suitable for applications in the field of nanobiotechnology. Two different approaches to reach this goal are presented and discussed: in the first approach, we use capillary forces to self-assemble silica nanoparticles on a wettability contrast pattern by controlled drying and evaporation. This allows the efficient patterning of a variety of nanoparticle systems and—under certain conditions—leads to the formation of novel branched structures of colloidal lines, that might help to elucidate the formation process of these nanoparticle arrays. The second approach uses a recently developed chemical patterning method that allows for the selective immobilization of functionalized sub-100 nm particles at distinct locations on the surface. In addition, it is shown how these nanocolloidal micro-arrays offer the potential to increase the sensitivity of existing biosensing devices. The well-defined surface chemistry (of particle and substrate) and the increased surface area at the microspots, where the nanoparticles self-assemble, make this patterning method an interesting candidate for micro-array biosensing.