“Writing” Crystal Phases in Amorphous Calcium Carbonate via Laser‐Induced Patterned Transformations

Abstract Biomineralization demonstrates nature's remarkable ability to precisely regulate mineral formation, controlling both polymorph selection and spatial organization. This fascinating level of precision has inspired the investigation into spatially controlled, laser‐induced crystallization. To this end, laser‐induced patterned crystallization is employed within a Magnesium (Mg)‐stabilized amorphous calcium carbonate (ACC) matrix, generating four distinct phases: calcite, stable dehydrated ACC, monohydrocalcite, and hydromagnesite. The parameters affecting phase formation are investigated and it is determined that they are governed by laser power and scanning rate. Calculations allow the determination of the temperature generated under these conditions, spanning a range of laser powers and scan rates, leading to the development of a model explaining the formation of each phase. It allows to reproducibly “write” crystal phases on the surface in a spatially controlled and rationally designed manner. The research presents a novel approach to laser‐induced spatial patterning of multiple crystallographic phases through an amorphous precursor, opening new avenues for bio‐inspired studies and offering fresh insights into crystallization mechanisms from amorphous precursors. The capabilities demonstrated herein enable precise phase control through the implementation of “writing crystallography,” offering potential applications in advanced additive manufacturing techniques and single‐layer patterning.