  We investigated the electrostatic behavior of ferroelectric liquid droplets
exposed to the pyroelectric field of a lithium niobate ferroelectric crystal
substrate. The ferroelectric liquid is a nematic liquid crystal in which almost
complete polar ordering of the molecular dipoles generates an internal
macroscopic polarization locally collinear to the mean molecular long axis.
Upon entering the ferroelectric phase by reducing the temperature from the
nematic phase, the liquid crystal droplets become electromechanically unstable
and disintegrate by the explosive emission of fluid jets. These jets are mostly
interfacial, spreading out on the substrate surface, and exhibit fractal
branching out into smaller streams to eventually disrupt, forming secondary
droplets. We understand this behavior as a manifestation of the Rayleigh
instability of electrically charged fluid droplets, expected when the
electrostatic repulsion exceeds the surface tension of the fluid. In this case
the charges are due to the bulk polarization of the ferroelectric fluid which
couples to the pyroelectric polarization of the underlying lithium niobate
substrate through its fringing field and solid-fluid interface coupling. Since
the ejection of fluid does not neutralize the droplet surfaces, they can
undergo multiple explosive events as the temperature decreases.
