  Different contact regimes between a spherical lens and a periodically
patterned substrate are observed, when they are pressed against each other. Top
contact occurs when only the highest substrate sections touch the lens, whereas
mixed contact implies that both the highest and the lowest substrate sections
come into contact with the lens. In this paper, we study how the pattern
density of the substrate, along with its physical properties and those of the
lens, determine the transition from top contact to mixed contact. Experiments
and numerical simulations had been performed, as complementary approaches to
obtain data, and a theoretical analysis has been developed to gain insight on
the effect of the physical parameters on the contact transition. As a result, a
phase diagram is presented, in terms of the load and the contact radius, that
combines the observations of the three approaches (experimental, numerical, and
theoretical), unveiling the boundaries of three contact regimes: (1)
deterministic-driven contact, (2) top contact, and (3) mixed contact.
