In this paper, we demonstrate a technique to fabricate nanostructure in an inexpensive way. A layer of polystyrene (PS) beads (650 nm diameter) was coated to get monolayer on silicon oxide substrate. The gap created between the aligned PS beads was used to deposit metals like Cr, Al, and Au using sputtering and e-beam evaporation techniques. The nano sphere acted as a mask to generate array of metallic nano structures. The thickness of deposited metal was varied to achieve varying height of the structures. Removal of the PS beads was done using di-chloromethane. Silicon oxide substrate along with the regularly aligned metallic nano structure thus formed, acted as a metallic mould for nanoimprinting. The pattern was then imprinted on a thin PMMA layer. Nano cavities created on the PMMA layer were of the order of metallic nano structure. Spot lithography was used to create rectangles to define the regions (or spots) of confinement for nanosphere. These regular nano pattern generated could be optimized to get good quality nano structures and has apparent application in photonic crystal formation and other nano application.
Fabrication of microlens array using polymer reflow is beginning to be a mainstream process, whether the polymer is directly used or whether the spherical profile is transferred by plasma etching to a glass substrate as, for example, in some handphone cameras. The focus so far has been on uniformity and obtaining lenses with equal radius and equal focal length. Actually it is easy to show using a phenomenological model that the focal length is depending on the lens radius, and not much on the contact angle, an effect that can be traced to the line tension force. For a biomedical application we need to terminate a 600um diameter imaging fiber with a group of lenses of different diameters - but with similar focal length. We have devised a microfabrication process on a silicon wafer to produce the lens with variable diameter and identical focal length, while etching the silicon wafer has helped us producing a sheath to insert the optical fiber and mount the lenses on the optical fiber.