Fabrication of large arrays of plasmonic nanostructures via double casting

Large arrays of periodic nanostructures are widely used for plasmonic applications, including ultrasensitive particle sensing, optical nanoantennas, and optical computing; however, current fabrication processes (e. g., e-beam lithography and nanoimprint lithography) remain time consuming and expensive. Previously, researchers have utilized double casting methods to effectively fabricate large-scale arrays of microscale features. Despite significant progress, employing such techniques at the nanoscale has remained a challenge due to cracking and incomplete transfer of the nanofeatures. To overcome these issues, here we present a double casting methodology for fabricating large-scale arrays of nanostructures. We demonstrate this technique by creating large (0.5 cm x 1 cm) arrays of 150 nm nanoholes and 150 nm nanopillars from one silicon master template with nanopillars. To preclude cracking and incomplete transfer problems, a hard-PDMS/soft-PDMS (h-PDMS/s-PDMS) composite stamp was used to replicate the features from: (i) the silicon template, and (ii) the resulting PDMS template. Our double casting technique can be employed repeatedly to create positive and negative copies of the original silicon template as desired. By drastically reducing the cost, time, and labor associated with creating separate silicon templates for large arrays of different nanostructures, this methodology will enable rapid prototyping for diverse applications in nanotechnological fields.