Packing of submicrometer-sized polystyrene particles within the micrometer-sized recessed patterns on silicon substrate

The packing of submicrometer-sized polystyrene particles within the micrometer-sized recessed patterns were achieved using silicon-microfabricated substrates and a simple dipping and pulling-up process. The polystyrene particles were selectively deposited within the micrometer-sized square, triangular, or circular recessed patterns by tuning the experimental conditions during the pulling-up process. The process produced a capillary force, i.e., a gas-liquid interfacial tension, to push the particles into the recessed patterns on the substrate. In most cases, the selectively depositing particles within the recessed patterns self-organically formed the closest packing structures. However, a special phenomenon, cubic packing structures of the particles, was observed when using square patterns with a few times larger side-length than the particle diameters. Several particle packing structures within different-sized square patterns were demonstrated, and the relationship between the particle packing structures and square pattern sizes were discussed.