Micropatterning of block copolymer micelle thin films using solvent capillary contact printing

This paper describes a new and facile method, 'solvent capillary contact printing (SCCP)', that fabricates micro-patterned hydrophilic/hydrophobic surface caused by the selective manipulation of nanometre-scale block copolymer micelles. The method is based on using capillary injection and evaporation of a solvent, which is preferential to a core block of micelles, through poly(dimethylsiloxane) (PDMS) microchannels placed on a pre-formed block copolymer micelle monolayer. We produced well-defined surface micropatterns where a nanostructure consisting of core-opened micelles gave rise to hydrophilic surface property in the regions in contact with solvent while one consisting of hemispherical micelles remained hydrophobic in the regions contacted by the PDMS mould. Our method allows repetitive micropatterning; a surface micropattern previously formed is simply erased by exposure of preferential solvent vapour due to reversible structure modification of micelles. Furthermore, SCCP with various metal salts, precursors of metal nanoparticles, enables us to fabricate micropatterned arrays of well-separated metal nanoparticles which can be used as a catalyst for synthesizing nanowires. The micropatterned arrays of GaN nanowires are demonstrated, fabricated by SCCP.