Geometrical dynamics of edge-driven surface growth

TL;DR

This paper develops a geometric mathematical framework to understand the shape and growth dynamics of edge-driven surface structures observed in various physical and biological systems, linking surface morphology with evolving space curves.

Contribution

It introduces a novel set of equations describing the geometrical dynamics of growth fronts as space curves, applicable to a wide range of thin-walled morphologies.

Findings

Captures diverse precipitate patterns across scales

Provides a new geometric framework for surface growth

Suggests a class of dynamical systems with non-Euclidean surfaces

Abstract

Accretion of mineralized thin wall-like structures via localized growth along their edges is observed in a range of physical and biological systems ranging from molluscan and brachiopod shells to carbonate-silica composite precipitates. To understand the shape of these mineralized structures, we develop a mathematical framework that treats the thin-walled shells as a smooth surface left in the wake of the growth front that can be described as an evolving space curve. Our theory then takes an explicit geometric form for the prescription of the velocity of the growth front curve, along with some compatibility relations and a closure equation related to the nature of surface curling. The result is a set of equations for the geometrical dynamics of a curve that leaves behind a compatible surface. Solutions of these equations capture a range of geometric precipitate patterns seen in abiotic and biotic forms across scales. In addition to providing a framework for the growth and form of these thin-walled morphologies, our theory suggests a new class of dynamical systems involving moving space curves that are compatible with non-Euclidean embeddings of surfaces.