Two-dimensional self-assembly of spherical particles using a liquid mold and its drying process

We developed a novel process to fabricate particle wires through self-assembly on hydrophilic regions of SAMs (self-assembled monolayer). A SAM of octadecyltrichlorosilane was formed on a silicon substrate and modified by UV irradiation to create a pattern of hydrophobic octadecyl and hydrophilic silanol groups. Ethanol or water containing particles (550 or 800 nm diameter) were dropped onto a patterned SAM. The solution was separated into two droplets with a liquid bridge between the droplets along the hydrophilic regions of a patterned SAM. The droplets and the liquid bridge were used as a mold for fabrication of a two-dimensional pattern of colloid,crystals. Particle wire was formed between two droplets and colloid crystals such as an opal structure were formed at both ends of the particle wire after drying the solution. The particle wires constructed from a close-packed structure or non-close-packed structure, i.e., square lattice, were fabricated through self-assembly at room temperature using this method.