Plasmonic structures self-assembled by glancing angle deposition for optofluidic devices

Abstract

In this study, we experimentally demonstrate the self-assembly of gold micropetals and microfluidic control thereof using their thermoplasmonic properties. To this end, gold micropetals were fabricated on a glass substrate via glancing angle deposition and microsphere lithography techniques. Each micropetal consisted of two portions with thin gold films of different thicknesses, resulting in an intrinsic optical absorption distribution. A water vapor microbubble was generated at the region of high optical absorption of the gold micropetal immersed in degassed water via irradiation from a CW laser. Subsequently, the thickness distribution on the micropetal yielded an effective temperature gradient along the substrate surface. Resultantly, the primary water stream around the bubble was tilted by ~45° from the surface normal. The micropetal is thus shown to be useful for providing a specific temperature gradient around the microbubble and generating a flow in the desired direction under the conditions of simple laser irradiation.