  When a fluid-immersed array of lamellae or filaments that is attached to a
substrate is dried, evaporation leads to the formation of menisci on the tips
of the plates or pillars that bring them together. Similarly, when hair dries
it clumps together due to capillary forces induced by the liquid menisci
between the flexible hairs. Building on prior experimental observations, we use
a combination of theory and computation to understand the nature of this
instability and its evolution in both the two-dimensional and three-dimensional
setting of the problem. For the case of lamellae, we explicitly derive the
interaction torques based on the relevant physical parameters. A Bloch-wave
analysis for our periodic mechanical system captures the critical volume of the
liquid and the 2-plate-collapse eigenmode at the onset of instability. We study
the evolution of clusters and their arrest using numerical simulations to
explain the hierarchical cluster formation and characterize the sensitive
dependence of the final structures on the initial perturbations. We then
generalize our analysis to treat the problem of pillar collapse in 3D, where
the fluid domain is completely connected and the interface is a surface with
the uniform mean curvature. Our theory and simulations capture the salient
features of both previous experimental observations and our own in terms of the
key parameters that can be used to control the kinetics of the process.
