Phase-field modeling of biomineralization in mollusks and corals: Microstructure vs. formation mechanism

TL;DR

This paper adapts phase-field modeling from materials science to simulate mesoscale biomineralization in mollusks and corals, successfully reproducing various microstructures and comparing classical and non-classical calcification mechanisms.

Contribution

It demonstrates the applicability of phase-field theory to biological mineralization, modeling diverse microstructures and elucidating underlying formation mechanisms.

Findings

Microstructures similar to natural biominerals can be simulated.

Non-classical calcification route has a more realistic timescale.

Phase-field modeling can reveal underlying design principles of biomineralization.

Abstract

While biological crystallization processes have been studied on the microscale extensively, models addressing the mesoscale aspects of such phenomena are rare. In this work, we investigate whether the phase-field theory developed in materials science for describing complex polycrystalline structures on the mesoscale can be meaningfully adapted to model crystallization in biological systems. We demonstrate the abilities of the phase-field technique by modeling a range of microstructures observed in mollusk shells and coral skeletons, including granular, prismatic, sheet/columnar nacre, and sprinkled spherulitic structures. We also compare two possible micromechanisms of calcification: the classical route via ion-by-ion addition from a fluid state and a non-classical route, crystallization of an amorphous precursor deposited at the solidification front. We show that with appropriate choice of the model parameters microstructures similar to those found in biomineralized systems can be obtained along both routes, though the timescale of the non-classical route appears to be more realistic. The resemblance of the simulated and natural biominerals suggests that, underneath the immense biological complexity observed in living organisms, the underlying design principles for biological structures may be understood with simple math, and simulated by phase-field theory.