Three-dimensional sequential self-assembly of microscale objects

The control of the sequential self-assembly of microscale objects with two assembly steps by changing the pH of the solution is analyzed. The processes that can separate assembled structures with a specific length from the others are needed. Fluidic separators with microchannels that can distinguish microbeads with a specific size from the other beads by liquid flow can be used for the separation of the assembled microstructures. It is possible to increase the number of assembly steps by using surfaces that have different IEP values, such as nickel or modified surfaces with terminal-functionalized self-assembled monolayers (SAM), to advance sequential self-assembly. This self-assembly control mechanism can be widely applied to combining microfabricated objects with colloidal particles or biological molecules, since the interactions used in the self-assembly are also dominant in colloidal aggregation/dispersion or in biomaterials, such as for the conformation of protein molecules.