The dynamics of nacre self-assembly

Abstract

We show how nacre and pearl construction in bivalve and gastropod molluscs can be understood in terms of successive processes of controlled self-assembly from the molecular- to the macro-scale. This dynamics involves the physics of the formation of both solid and liquid crystals and of membranes and fluids to produce a nanostructured hierarchically constructed biological composite of polysaccharides, proteins and mineral, whose mechanical properties far surpass those of its component parts.

Nanostructure and crystallography of aberrant columnar vaterite in Corbicula fluminea (Mollusca)

“…The observed domains are usually enclosed in a cortex of lower density material, probably an amorphous organo-mineralic matrix (Baronnet et al, Due to the ubiquitous occurrence of isomorphic nanostructural relations in all molluscan systems, their microstructures are generally thought to be formed according to the same fundamental mechanism. The most widely investigated type of molluscan shell is most certainly nacre, the nanodomain structure of which is now considered to be the result of the formation of individual tablets by the aggregation of vesicles filled with an organo-mineralic gel which crystallises upon emplacement at the growth front (Baronnet et al, 2008;Cartwright and Checa, 2007;Dauphin, 2008;Jacob et al, 2008;Rousseau et al, 2005). A heteroepitaxial nucleation mechanism related to the organic material within these vesicles, rather than the organic sheaths enveloping the tablets, is thought to be responsible for the perfect crystallographic continuity across different nanodomains within a tablet Rousseau et al, 2005).…”

“…It is well known that the single crystalline microstructural units constituting the various types of mollusc shell are partitioned on submicron length scales into irregular rounded domains, usually tens to sometimes hundreds of nanometres in size (Baronnet et al, 2008;Cartwright and Checa, 2007;Dauphin et al, 2003;Dauphin, 2008;Jacob et al, 2008;Rousseau et al, 2005;Soldati et al, 2008). This partitioning can only rarely be observed with electron microscopic techniques (Erben and Watabe, 1974;Soldati et al, 2008;Wilmot et al, 1992), however, and is much more clearly seen using atomic force microscopy (AFM) (Baronnet et al, 2008;Dauphin et al, 2003;Dauphin, 2008;Jacob et al, 2008;Rousseau et al, 2005).…”

“…The detailed characterisation of biomineralised structures on the micro-and nanometre scales is of great interest to the Materials and Earth science communities alike since it might lead to a better understanding of their mode(s) of formation (Cartwright and Checa, 2007;Erben and Watabe, 1974;Jacob et al 2008). This might in turn allow the development of new, highly advanced materials (Noll et al, 2002;Tang et al, 2003) and has a bearing on the fractionation of stable isotopes used in palaeoclimate reconstructions (Cohen and McConnaughey, 2003;Erez, 2003;Weiner and Dove, 2003).…”

Spiral and target patterns in bivalve nacre manifest a natural excitable medium from layer growth of a biological liquid crystal

“…2 for a sketch of bivalve molluscan anatomy and nacre structure.) From an examination of the extrapallial space of the bivalve mollusk, the narrow liquid-filled cavity between the soft tissues and the shell of the organism, it is seen that the first visible feature in nacre growth is the formation of a new interlamellar membrane in the fluid (2)(3)(4). In Fig.…”

“…This is concurrently transformed with the addition of proteins and aragonite into the solid biocomposite that is nacre; a process that we analyze in depth in ref. 2. Here, we concentrate on understanding the mode of liquid-crystal construction used by the mollusk, in which it is built up layer by layer.…”