  Surface stress drives long-range elastocapillary interactions at the surface
of compliant solids, where it has been observed to mediate interparticle
interactions and to alter the transport of liquid drops. We show that such an
elastocapillary interaction arises between neighboring structures that are
simply protrusions of the compliant solid. For compliant micropillars arranged
in a square lattice with spacing p less than an interaction distance p*, the
distance of a pillar to its neighbors determines how much it deforms due to
surface stress: pillars that are close together tend to be rounder and flatter
than those that are far apart. The interaction is mediated by the formation of
an elastocapillary meniscus at the base of each pillar, which sets the
interaction distance and causes neighboring structures to deform more than
those that are relatively isolated. Neighboring pillars also displace toward
each other to form clusters, leading to the emergence of pattern formation and
ordered domains.
