  The rapid and complex patterning of biosilica in diatom frustules is of great
interest in nanotechnology, although it remains incompletely understood.
Specific organic molecules, including long-chain polyamines, silaffins, and
silacidins are essential in this process. The molecular structure of the
synthesized polyamines significantly affects the quantity, size, and shape of
silica precipitates. Experimental findings show that silica precipitation
occurs at specific phosphate ion concentrations. We focus on the hypothesis
that pattern formation in diatom valve structures is driven by phase separation
of species-specific organic molecules. The resulting organic structures serve
as templates for silica precipitation. We investigate the role of phosphate
ions in self-assembly of organic molecules and analyze how the reaction between
them affects the morphology of the organic template. Using mathematical and
computational techniques, we gain an understanding of the range of patterns
that can arise in a phase-separating system. By varying the degree of
dissociation and the initial concentrations of reacting components we
demonstrate that the resulting geometric features are highly dependent on these
factors. This approach provides insights into the parameters controlling
patterning. Additionally, we consider the effects of prepatterns, mimicking
silica ribs that preexist the pores, on the final patterns.
