MIT researchers uncover the secrets behind a marine creature's defensive armor -- 1 that is exceptionally tough, yet optically clear
The shells of a sea creature, the mollusk Placuna placenta, are not only exceptionally tough, but also clear enough to read through. Now, researchers at MIT have analyzed these shells to determine exactly why they are so resistant to penetration and damage — even though they are 99 percent calcite, a weak, brittle mineral.
The shells' unique properties emerge from a specialized nanostructure that allows optical clarity, as well as efficient energy dissipation and the ability to localize deformation, the researchers found. The results are published this week in the journal Nature Materials, in a paper co-authored by MIT graduate student Ling Li and professor Christine Ortiz.
Ortiz, the Morris Cohen Professor of Materials Science and Engineering (and MIT's dean for graduate education), has long analyzed the complex structures and properties of biological materials as possible models for new, even better synthetic analogs.
Engineered ceramic-based armor, while designed to resist penetration, often lacks the ability to withstand multiple blows, due to large-scale deformation and fracture that can compromise its structural integrity, Ortiz says. In transparent armor systems, such deformation can also obscure visibility.
Creatures that have evolved natural exoskeletons — many of them ceramic-based — have developed ingenious designs that can withstand multiple penetrating attacks from predators. The shells of a few species, such as Placuna placenta, are also optically clear.
To test exactly how the shells — which combine calcite with about 1 percent organic material — respond to penetration, the researchers subjected samples to indentation tests, using a sharp diamond tip in an experimental setup that could measure loads precisely. They then used high-resolution analysis methods, such as electron microscopy and diffraction, to examine the resulting damage.
The material initially isolates damage through an atomic-level process called "twinning" within the individual ceramic building blocks: Part of the crystal shifts its position in a predictable way, leaving two regions with the same orientation as before, but with one portion shifted relative to the other. This twinning process occurs all around the stressed region, helping to form a kind of boundary that keeps the damage from spreading outward.
The MIT researchers found that twinning then activates "a series of additional energy-dissipation mechanisms … which preserve the mechanical and optical integrity of the surrounding material," Li says. This produces a material that is 10 times more efficient in dissipating energy than the pure mineral, Li adds.
The properties of this natural armor make it a promising template for the development of bio-inspired synthetic materials for both commercial and military applications — such as eye and face protection for soldiers, windows and windshields, and blast shields, Ortiz says.
The work was supported by the National Science Foundation; the U.S. Army Research Office through the MIT Institute for Soldier Nanotechnologies; the National Security Science and Engineering Faculty Fellowships Program; and the Office of the Assistant Secretary of Defense for Research and Engineering.
Written by David Chandler, MIT News Office
Andrew Carleen | EurekAlert!
Engineers develop smart material that changes stiffness when twisted or bent
15.02.2018 | Iowa State University
Breaking local symmetry: Why water freezes but silica forms a glass
14.02.2018 | Institute of Industrial Science, The University of Tokyo
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).
Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
16.02.2018 | Information Technology
16.02.2018 | Health and Medicine
16.02.2018 | Physics and Astronomy