Multi-scale structure of the Pinctada mother of pearl: Demonstration of a continuous and oriented organic framework in a natural ceramic

Sheet nacre is a promising natural bioceramic, which consists on the internal lustrous "mother of pearl" layer of many molluscan shells, e.g. Pinctada, our model. The aim of this work is to study the structure of the flat polygonal tablets of nacre, in order to understand the multi-scale organization of this composite material and the role of the organic template during the growth of the biocrystal. We studied the organic matrix, in situ with techniques such as darkfield transmission electronic microscopy (TEM) on small cross-sections of nacre of Pinctada maxima, or intermittent-contact atomic force microscopy coupled with phase imaging on samples of nacre of Pinctada margaritifera polished parallel to the surface of the tablets. In this study, we demonstrate the continuity of the organic framework and the crystallographic orientation in the biocrystal at 2 relevant levels nano- and micro-scale.