Self-Assembly of Spherical Colloidal Photonic Crystals inside Inkjet-Printed Droplets

Abstract

The manufacturing of three-dimensional colloidal structures on solid substrates is an important topic of applied research, aiming for photonic components especially in photovoltaic and sensor applications. Whereas conventional techniques such as wet self-assembly are based on engineering of the substrate surface energy, alternative strategies envisage the independence of the interfacial conditions. We report on inkjet printing of colloidal suspensions of monodisperse silica or polystyrene nanoparticles or both and their self-assembly to spherical colloidal photonic crystals. The formation process of the colloidal nanoparticles into stable spherical colloidal assemblies (SCAs) is achieved by a self-assembly process inside tiny droplets of a stochastic mist generated intentionally instead of a jet of individual single droplets using inkjet printing. The mist-jetted, shrinking droplets serve as confined geometries for the solidification of the nanoparticles during the evaporation; thus the particles are pack...