Controlling Self-Assembled Periodic Structures of Colloidal Particles by Convective Self-Assembly

Abstract

Periodic structures of colloidal particles have attracted considerable interest because they are promising for a wide range of potential applications. Convective self-assembly of colloidal particles is a possible candidate because it is capable of fabricating ordered arrays in a simple manner at low-cost without any templates. We have succeeded in fabricating stripe pattern parallel to the air-solvent-substrate contact line and dot array pattern by using this technique. In the present study, we newly revealed the formation of stripe patterned structures perpendicular to the contact line by controlling the particle concentration and particle size. We found out that the vertical stripe pattern is formed when the particle size of 500 ‍nm is used under the concentration region between those for the horizontal stripe and dot array patterns. The width of the vertical stripes increases with the particle concentration, while the spacing between stripes remains unchanged against the concentration. Furthermore, we fabricated a peculiar hybrid pattern composed of vertical stripes and dot arrays by using a two-step convective self-assembly method, in which a vertical stripe pattern of 570 ‍nm silica particles was first prepared on a substrate, and the vertical stripe pattern was then immersed in a suspension of 120 ‍nm silica particles.