Depletion potentials between colloids and patterned surfaces

Effective interactions between the hard-sphere colloids and the patterned substrates created by depositing one or more hemispheres on the structureless walls are studied. The deposition of only one hemispherical cap gives rise to a new global minimum of the depletion potential but the difference from the planar hard wall case is moderate. On the other hand, when the hemispherical caps form a periodic array, multiple overlaps of the excluded volumes lead to formation of deep global minimum of the depletion potential. In some cases this minimum is deeper than 10kBT and this is more than triple of the potential minimum for the structureless wall. We conclude that templated surfaces affect depletion potentials significantly. This effect will have a major impact even when the residual attractive/repulsive interactions are present