Designing Multicolor Micropatterns of Inverse Opals with Photonic Bandgap and Surface Plasmon Resonance

Abstract

Structural coloration provides unique features over chemical coloration, such as nonfading, color tunability, and high color brightness, rendering it useful in various optical applications. To develop the structural colors, two different mechanisms of coloration-photonic bandgap (PBG) and surface plasmon resonance (SPR)-have been separately utilized. In this work, a new method is suggested to create structurally colored micropatterns by regioselectively employing SPR in a single film of inverse opal with PBG. The inverse opals are prepared by thermal embedding of opal into a negative photoresist and its subsequent removal. The inverse opals have a hexagonal array of open pores on the surface which serves as a template to make SPR-active nanostructures through a directional deposition of gold, a perforated gold film and an array of curved gold disks are formed. With a shadow mask lithographically prepared, the gold is regioselectively deposited on the surface of the inverse opal, which results in two distinct regions of gold-free inverse opal with PBG and gold nanostructure with SPR. As PBG and SPR develop their own structural colors respectively, the resultant micropatterns exhibit pronounced dual colors. More importantly, the micropatterns show the distinguished optical response for evaporation of volatile liquids that occupy the pores.