Fabrication of Binary Opal Lattices in Microfluidic Devices

We have studied growth and fabrication of opal lattices made from polystyrene and silica particles by an on-chip colloidal self-assembly (CSA) approach. An optical microscopy method was used to analyze the lattice growth behavior. A mathematical model was also adopted and modified to describe the growth behavior of the silica system. On the basis of these studies, silica and polystyrene systems demonstrate different growth dynamics that originate from a sedimentation process in the microfluidic chip reservoir fractionating large and small particles. Binary lattices of silica particles were fabricated by a periodic chip rotation method. The effect of particle number ratio on the opal stoichiometry was also studied for the polystyrene system. By increasing the number ratio from 2.5 to 11, different structural stoichiometries were achieved.