Fabrication of patternable nanopillars for microfluidic SERS devices based on gap-induced uneven etching

In this work, a lithography-free approach for fabricating patternable nanopillars is reported. The key technique of the approach is to introduce a gap over the substrate by covering it with a cap, which contains through holes and the material on its lower surface has similar etching rate with the substrate. By this means, uneven etching of the substrate is induced under the through holes, consequently, nanopillars are fabricated into patterns corresponding to the holes. By sputtering a thin layer of Ag on the nanopillar patterns, obvious Raman enhancement can be observed. Since the large areas around the patterns are protected from anisotropic etching and metal sputtering, they are flat enough to be bonded with PDMS caps thus to form microfluidic Surface-enhanced Raman Scattering devices, and the whole fabrication process for the devices is simplified.