Biomimetic Significance of the Nanofeatures and Nanomechanical Properties of Organic Thin Films in Nacre

Abstract

Many of important advances in materials engineering have come from transitioning to thinking of materials and their properties on the nano-scale rather than on the macro- or even micro-scale. Improvements in imaging technology have allowed us to see the nanofeatures that directly impact the chemical and mechanical properties of natural and man-made materials. This has been especially transformative to the study of the structure and failure modes of nacre, one of nature’s most impressive composites which provides inspiration to the field of biomimetics. Now that these characteristics can be quantified and these features can be imaged, for the first time scientists have begun to determine the importance of nanoasperities and structure of the organic layer in nacre. As technology evolves to let us examine materials on progressively smaller length scales, it follows that we would also develop techniques to manipulate structure and composition on the same. This project investigates the structure of the organic component of nacre; specifically its mechanical properties, self-assembly, and interactions with the inorganic layer. I began by motivating my research and placing it firmly in a literary context. Next, I used SEM and AFM to image the nacre samples both before and after plasma-etching. Plasma-etching has only recently begun to be applied to nacre and has not been previously used to investigate the organic layer. The plasma-etching allowed me to selectively remove organic components and document their relative placement in the organic layer. From there I proposed conclusions regarding nacre’s self-assembly with regard to its mechanical properties. I then applied these principles to explain the existence of the relatively less discussed “dome” platelets, to rationalize their role in the organic layer, and to analyze their potential benefits for biomimetic materials.