Selective gold nano-patterning on flexible polymer substrate via concurrent nanoimprinting and nanotransfer printing

We report a simple technique of selective gold nano-patterning on non-planar polycarbonate substrate by combining nanoimprinting and gold nanotransfer printing techniques in a single concurrent nano-patterning process: thermal nanoimprinting directly patterns a MPTMS (3-mercaptopropyl trimethoxysilane)-coated polycarbonate sheet to form the non-planar nanostructures using a gold-film deposited mold. Simultaneously, the gold-film from the mold is selectively transfer-printed either onto the protrusion or the base of the imprinted non-planar structures. This high nano-patterning selectivity is achieved due to a combined effect of a thiol-terminated MPTMS-gold surface chemistry, more importantly, aided by a surface area dependent differential work of adhesion. We show the high delineation of the patterned gold on the non-planar polycarbonate substrate of various geometries such as pillars, dimples, and gratings, down to nano-scale resolution (130 nm) as well as over micro-scale resolution (10 μm), thus demonstrating that this can be a generic metal patterning technique. Using this technique, we fabricate a metal nanowire grid polarizer to demonstrate a potential device application. The main advantage of this technique lies in its inherent self-aligned process that simplifies selective Au nano-patterning on non-planar polymer surfaces, which is otherwise difficult to be obtained using conventional patterning techniques.