Carmichael’s Concise Review Coming Events
2020 15th European Molecular Imaging Meeting – EMIM 2020
March 24–27, 2020 Thessaloniki, Greece
www.e-smi.eu/index.php?id=1976
FOM2020 – Focus on Microscopy
April 5–8, 2020 Osaka, Japan
http://focusonmicroscopy.org
2020 MRS Spring Meeting & Exhibit
April 13–17, 2020 Phoenix, AZ
www.mrs.org/spring2020
Microscopy & Microanalysis 2020
August 2–6, 2020 Milwaukee, WI
www.microscopy.org
emc2020: 17th European Microscopy Congress August 23–28, 2020 Copenhagen, Denmark
www.emc2020.eu
16th International Congress of Histochemistry and Cytochemistry (ICHC)
August 30–September 2, 2020 Prague, Czech Republic
http://ichc2020.com
Neuroscience 2020 October 24–28, 2020
Washington, DC
www.sfn.org/meetings/neuroscience-2020
2021
Microscopy & Microanalysis 2021 August 1–5, 2021
Pittsburgh, PA
www.microscopy.org
2022
Microscopy & Microanalysis 2022 July 31–August 4, 2022
Portland, OR
www.microscopy.org
2023
Microscopy & Microanalysis 2023 July 24–28, 2023
Minneapolis, MN
www.microscopy.org
2024
Microscopy & Microanalysis 2024 July 28–August 1, 2024
Cleveland, OH
www.microscopy.org
Figure 1: Highly deformed and recovered nacre. (Left) High-resolution S/TEM image of two tablets and their organic interface before compression. (Middle) Tablets heavily interlocked under 40 μN compressive load. (Right) After the indenter was retracted, the tablets and organic interface fully recovered their initial morphology. Field of view for all images is 400×465 nm.
8 doi:10.1017/S155192951900138X 2020 March Material scientists appreciate structures in nature that have exceptional mechan-
ical properties. Nature has optimized high-performance materials with unrivaled strength, toughness, and resilience using three-dimensional (3D) hierarchical archi- tectures that extend from the macro- down through micro- and nano-scale, and all the way to the atomic scale, with precision that human technology has yet to achieve. In fairness to material scientists, nature has had a few million years to work on this, whereas human endeavors only date back a couple thousand years or so. A recent example is the elegant study by an international group headed by
Jiseok Gim and Robert Hovden [1], who studied nanoscale deformation mechan- ics in dehydrated samples of nacre from the shell of a large Mediterranean clam (Pinna nobilis). Nacre, sometimes referred to as mother-of-pearl, lines the shells of most molluscs and is known to have excellent mechanical properties that could inspire new designs of structural materials. It is constructed from layered interdigitated polygonal (or pseudo-hexagonal) platelets and grains of aragonite (a form of calcium carbonate; CaCO3
Finding New Synthetic Routes to Complex Structural Materials
Stephen W. Carmichael Mayo Clinic, Rochester, MN 55905
carmichael.stephen@
mayo.edu
). Te platelets are 0.5 to 1 micron thick and
10 to 20 microns wide. Tey are bonded together by a thin (5 to 30 nanometer) layer of organic biopolymer material (the interlamellar membrane). Tere are also organic inclusions within the platelets. Te organic material accounted for about 3.4 percent of the nacre by weight, the remainder being aragonite. Gim et al. used high-resolution scanning/transmission electron microscopy
(S/TEM) combined with in situ nanoindentation in their studies. Tis allowed sub-nanometer resolution imaging of the deformation process and provided pre- cise assessment of when and where a fracture occurred in the nacre. During com- pression, the aragonite grains and organic inclusions reversibly rotate and deform, indicating nanoscale resilience of the nacre platelets. Te platelets lock to continu- ously redistribute stress across the organic interface. Remarkably, the completely locked interface recovers its original morphology without any deformation aſter the compression is released, and it retains its full mechanical strength.
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