Writing mesoscale patterns in block copolymer thin films through channel flow of a nonsolvent fluid

The authors demonstrate how a nonsolvent fluid, flowing over the surface of a block copolymer thin film in a complex path defined by a channel, can locally tailor the alignment of cylindrical microdomains. The cylinders have a periodicity of ∼30 nm, while the mesoscale pattern has a millimeter length scale. A diverging-converging channel is employed to measure alignment quality over a range of applied stresses in a single experiment; the results are compared with analogous measurements where the stress is applied through a controlled-stress rheometer, and can be satisfactorily described by a melting-recrystallization model.