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Abalone nacre is a multilayered ceramic/ organic composite (95 wt% calcium carbonate, 5 wt% organic material) that exhibits outstanding mechanical properties beyond those of the individual components. Understanding the structure-property relationship of this natural material can lead to the development of novel bioinspired laminates. Techniques such as nanoindentation, nanoscratch, electron and atomic force microscopy have been employed on the nacre and on the individual constituents (the isolated mineral and organic component) to reveal nanostructured features. We can now quantitatively determine the role they play in the overall toughening of the material.

Nanoscratch results: Optical micrograph, friction force curve, and SEM micrographs showing deformation mechanisms of untreated

nacre.   

Untreated

Deproteinized

Demineralized

AFM image showing a nanoindent on untreated nacre.

Different treatments performed on abalone nacre

Bioinspired synthesis of tough laminates Joanna M. McKittrick, University of California-San Diego, DMR 1006931

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Long bone axis

100 µm

Bovine cortical bone

µ-CT 3D isosurface images of untreated cortical bone showing the side view of canal network (red: Haversian, vertical; Volkmann’s, horizontal) and osteocyte lacunae (yellow); the lacunae are preferentially oriented in vertical direction, indicating the long axis of bone.

A theoretical multi-scale model that portrays the hierarchical structure of bone as a composite with interpenetrating biopolymers (collagen) and minerals (hydroxyapatite), together with void spaces (porosity), was used to predict the elastic response of cortical bone. The model involves a bottom-up approach and employs micromechanics and classical lamination theories. Porosity and microstructure were characterized using microscopy and micro-computed tomography. Experiments on cortical bone samples from bovine femur included completely demineralized and deproteinized bones as well as untreated bone samples. The characterization of structure and properties of these three bone states provides a deeper understanding of the contributions of the Individual components of bone to its elastic response.

We have started freeze-casting hydroxyapatite to form synthetic bone-inspired scaffolds.

Joanna M. McKittrick, University of California-San Diego, DMR 1006931

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Professor’s McKittrick research was introduced to

Future generations of scientists in the range from

elementary school to educational TV program nation

wide. Co-PI Prof. Marc Meyers, was featured on

the PBS NOVA program hosted by David Pogue,

“Making Stuff Stronger,” showing why the abalone

shell and Toco Toucan beak are so tough despite the

relatively weak properties of their main constituents

(calcium carbonate for abalone shell and simple

keratin structure for toucan beak). It was shown and

discussed that unique properties of biological

materials are the result of sophisticated structures

designed by the millions of years of evolution.

Millions of today’s and future scientists all over the

country were able to watch this program.

Prof. Meyers was interviewed by the NOVA Science TV Program with host David Pogue and director in Emerald Forest Bird Gardens with two toucans in the background.

http://www.pbs.org/wgbh/nova/tech/making-stuff-stronger.html

Bioinspired synthesis of tough laminates Joanna M. McKittrick, University of California-San Diego, DMR 1006931