(593g) Ultrasonic Assisted Self-Assembly of Polystyrene Nanospheres

Nanosphere lithography is an inexpensive technique aimed at providing a versatile two-dimensional template for the rapid-scalable manufacturing of nanostructures. Colloidal self-assembly, a method by which colloidal particles assemble themselves into crystalline structures, is among the many techniques employed for the construction of such 2D templates. Recently developed self-assembly methods have been directed at optimizing the monolayer-making process in terms of reproducibility and production speed, but a significant limitation in terms of nanoscale order persists. As ordering bears a direct effect on the quality of subsequently-produced nanostructures, optimizing this feature is extremely critical.

Here, we show that exposing a polystyrene nanosphere close-packed array at the air-water interface to capillary waves reduces the number of defects and produces ordered regions over cm² areas. This reordering of particles occurs at broad-ranged low-frequency capillary waves induced via megahertz sonication. In addition to constructing monolayers with minimized defects, our method is fast generating 100 cm² area monolayers of 500 – 800 nm diameter polystyrene spheres in under two minutes.

We will compare arguments for the minimization of monolayer defects when coupled with sonication and propose that low-frequency capillary waves are the primary method that promotes particle re-ordering.