A large uniform monolayer area obtained by droplet evaporation in microwells

Nanosphere lithography has potential in many areas, and there have been many methods that deposit the colloidal suspension onto the substrate. However, it is important and still difficult to control the uniformity of the monolayer on a plane substrate. In this study, we have found a method for a uniform monolayer of polystyrene beads by confining the droplets with microwells. By simply controlling the droplet size and the colloidal concentration, the largest monolayer area could be obtained. In our application, the monolayer of polystyrene beads on substrate was used as a mask through which gold films were deposited. After removal of the polystyrene beads, an array of triangular Au patterns was left on the substrate. These samples were subsequently annealed, which resulted in gold nanoparticles arrays.