Marangoni effects on evaporative lithographic patterning of colloidal films.

We investigate the effects of Marangoni stresses on the evaporative lithographic patterning of colloidal films (Harris, D. J.; Hu, H.; Conrad, J. C.; Lewis, J. A. Phys. Rev. Lett. 2007, 98 (14), 148301). Films are dried beneath a mask that induces periodically varying regions of free and hindered evaporation. Direct imaging reveals that silica microspheres suspended within an organic solvent exhibit recirculating flows induced by temperature and surface tension gradients that arise during drying. The films display remarkable pattern formation with a majority of the particles deposited in the masked regions. Above a critical colloid volume fraction, recirculating flows are suppressed, leading to particle deposition in unmasked regions of high evaporative flux.