  The instabilities of fluid interfaces represent both a limitation and an
opportunity for the fabrication of small-scale devices. Just as non-uniform
capillary pressures can destroy micro-electrical mechanical systems (MEMS), so
they can guide the assembly of novel solid and fluid structures. In many such
applications the interface appears during an evaporation process and is
therefore only present temporarily. It is commonly assumed that this
evaporation simply guides the interface through a sequence of equilibrium
configurations, and that the rate of evaporation only sets the timescale of
this sequence. Here, we use Lattice-Boltzmann simulations and a theoretical
analysis to show that, in fact, the rate of evaporation can be a factor in
determining the onset and form of dynamical capillary instabilities. Our
results shed light on the role of evaporation in previous experiments, and open
the possibility of exploiting diffusive mass transfer to directly control
capillary flows in MEMS applications.
