Designing of photonic nanostructures using photocurable suspension of colloids

Abstract

Colloidal photonic crystals have been studied intensively for diverse applications because of their unique optical properties from their three-dimensional periodic nanostructures. In this thesis, I deal with the synthesis of responsive colloidal photonic microparticles with anisotropic shapes and optical properties based on the microfluidic approach and discuss for its potential applications. In Chapter 2, I report the microfluidic molding-featured microparticles with 3D internal periodic nanostructures using elastomeric membrane with negative relieves. The elastomeric membrane, separating flow channel and control channel, confines a photocurable suspension of silica particles into the negative relieves as it acts as monolithic microvalves. Upon pressurization of the monolithic microvalve, the membrane collapses on the bottom of flow channel, thereby making ultra-thin film of suspension in all area except the negative relieves. Therefore, UV irradiation on the valve polymerizes the resin only in the relieves, while ultra-thin film remains in a liquid state due to oxygen-inhibition. The polymerized microparticles are released from the mold by returning the valve off and flow through the bottom channel. In this method, microparticle shape is determined by that of the mold; this enables the featuring of microparticles with not only flat surface but even curved shape or potentially complex pattern depending on the shape of mold. In addition, silica particles in the resin form 3D arrays, which provide structural colors through constructive interference. The colors can be more pronounced by selectively removing silica particles. Moreover, incorporation of magnetic particles leads to magnetic functionality, providing remote controllability over rotational motion of photonic microparticles. In Chapter 3, I report the microfluidic designing-featured microcylinders with multiple distinct structural colors and magnetic functionality. To carry multiple optical propertie...