From micro-patterns to nano-structures by controllable colloidal aggregation at air-water interface

In this paper, we discuss a method to transform traditional-lithography micro patterns into nano-structures by self-assembly of nano-beads. In our approach, the destined substrate is prepared with hydrophilic micro patterns on hydrophobic background. Colloid with nano-beads wets exclusively the hydrophilic patterns due to interfacial forces when passing through air-water interface. After evaporation of water from the colloid, three-dimensional nano-bead structures are formed. A geometric model is proposed to describe this self-assembly process and its dependence on bead size, concentration, and pattern geometry, which can provide control over the aggregation of three-dimensional nano-structures.