Writing Mesoscale Patterns in Block Copolymer Thin Films

While a variety of methods have been developed to synthesize nanoscale objects, a major challenge remains to arrange these objects into arrays according to a user-defined pattern. Often, these patterns have “mesoscale” features: bigger than the nanoscale objects, but smaller than the array itself. PCCM researchers have recently developed a method for arranging the nanoscale cylinders present in block copolymer thin films into such mesoscale patterns. The method uses the flow of a nonsolvent fluid (silicone oil) over the film surface, following a path defined by a flow channel, and requires only the very simple apparatus shown in the figure. By manipulating the fluid flowrate, or changing the temperature relative to the block copolymer’s order-disorder transition temperature, the alignment quality can be easily controlled.