Fabrication of microfluidic devices with built-in periodic nanostructures for optofluidic integration

Abstract

Materials with periodic nanostructures have a variety of uses due to their physical and chemical properties as well as their unique morphology. Catalytic support, tissue/cell culture and diagnostic assay systems are the well known applications of those structures. Especially, 2D and 3D periodic structures with photonic properties have received enormous attention as a basic substrate for future photonic devices. Periodic nanostructures composed of noble metals have strong localization and enhancement of electromagnetic field at the surface. From such origin, 1D and 2D periodic metal nanostructures have surface plasmon resonance (SPR) or surface enhanced Raman scattering (SERS) properties applicable to biosensors and plasmonic devices. Dielectric materials with 2D or 3D periodicity may have photonic bandgap (PBG) property. The electromagnetic wave which has frequency correspond to the PBG of given nanostructures cannot exist inside of them. It means that the white light (or electromagnetic waves with broadband spectrum) shinning on the PBG structures can be reflected selectively. It is well known that the PBG property (or selective reflection) of material is governed by several variables such as the lattice constant, crystal orientation and refractive index contrast between the structure and medium. Here, I described a simple and facile bottom-up method for the fabrication of those multidimensional periodic nanostructures in the basis of colloidal self-assembly. Using selective photon-induced polymerization in colloidal crystal films, those nanoscale periodic structures can be patterned in micrometer scale. As well as the shape of resulting colloidal crystal patterns, their PBG properties could be tuned by pore size modulation. In addition, large-scale colloidal crystal films were generated by spin-coating of silica/ETPTA suspension. Holographic lithography (HL) was used as a top-down approach for the fabrication of multi-dimensional nanometer-scale period...