Gold Nanocups Fabricated Using Two-Dimensional Colloidal Crystals and Simulation of Their Optical Trapping Force

Optical tweezers are powerful and flexible tools for manipulating micrometre-sized objects. Recently, metal nanostructures are gathering attention to trap nanometre-sized objects to utilize their plasmonic properties. Here, we discuss the preparation of gold nanocups (250-nm diameter) and their plasmonic properties for optical trapping. Gold was sputtered on a two-dimensional colloidal crystal (2DCC) and then de-coupled from the 2DCC via hydrofluoric acid etching, which resulted in a uniform gold nanocup array that was encapsulated in a flexible polymer resin. These nanocups in a resin can be transferred onto a variety of substrates. The optical trapping properties of gold nanocups are also discussed.