Patterned crystallization of calcite in vivo and in vitro

Biologically formed calcite crystals have unique, sculptured shapes that are believed to be regulated locally by speci"c macromolecules and by directional #ux of ions into the microenvironment of crystal growth. This paper describes a biologically inspired synthesis of patterned calcitic "lms using micropatterned self-assembled monolayers (SAMs) which served as spatially constrained microenvironments for crystallization. The approach is based on the ability to govern mass transport to di!erent regions of the surface at a micron scale, by patterning rapidly nucleating regions (carboxylate-terminated SAMs) in regions that are slowly nucleating (methyl-terminated SAMs) and by regulating their sizes, geometry and concentration of the crystallizing solution. The ion #ux into the regions of crystal growth keeps the crystallizing solution over slowly nucleating regions undersaturated. Crystallization is then entirely restricted to the carboxylate-terminated regions of SAMs and results in the formation of large-area, high-resolution inorganic replicas of the underlying organic patterns. ( 2000 Elsevier Science B.V. All rights reserved.