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 −10k_BT 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.