Materials scientists are studying the structure of seashells to design stronger materials.
Engineering ideas from snails. I’m Bob Hirshon and this is Science Update.
Every seashell is a structure honed by millions of years of evolution to protect a soft creature from predators and the crushing forces of waves and water pressure. Rice University materials scientist Chandra Sekhar Tiwary says different demands led to different designs.
So if you have high pressure or a more harsh environment, you have a different shape. So you have a huge variety of shells depending on the environment.
In the journal Science Advances, Tiwary and his colleagues take a close look at two kinds of shell: a hinged clam like design, and a long spiral. They tested actual shells and 3-D printed versions to learn how their shapes and structural elements direct forces away from the animal inside. Analysis of these elegant and economical designs could be useful in everything from packaging to architecture. I’m Bob Hirshon, for AAAS, the science society.
Making Sense of the Research
Inspired by the strength of seashells, engineers at the Indian Institute of Science and Rice University set out to discover how the shells work in the hopes of being able to apply what they learn to defense and safety, automobiles, and architecture. The researchers, led by Chandra Sekhar Tiwary, a graduate student at the Indian Institute of Science and a visiting student at Rice, are studying molluscs, in particular, to learn how their complex exteriors evolved to protect them in harsh conditions. The ultimate goal is to see how their mechanical principles may be adapted for use in human-scale structures like vehicles and even buildings.
In order to carry out their research, the team decided to examine two types of molluscs: bivalves with two separate exoskeleton components joined at a hinge (as in clamshells) and terebridae that conceal themselves in screw-shaped shells. The shells themselves are made out of nacre, also known as mother-of-pearl, a strong and resilient matrix of organic and inorganic materials. The team then developed computer models of the two types of shells and printed 3-D models of them. To test the strength of the real shells and the models, they ran stress tests to discover how they remain stable and redirect stress to minimize damage when failure is imminent.
What the researchers discovered is that the shells' distinctive shapes make the them nearly twice as good at bearing loads than nacre alone. The clamshell's semicircular shape and curved ribs forced stress to the hinge while the screw-shaped shells directed the force toward the center and then the wide top. In both cases, the design of the shells only allowed fractures to appear where they would do the least harm to the organism inside.
What is the importance of this research? Even though engineers have made use of other designs from nature, like bird beaks and spider webs, to learn how to make stronger human-made materials, they haven't been able to use seashell designs because replicating the designs wasn't easy. With the advent of 3-D printers, however, replicating the shapes with materials tough enough to withstand the same forces has become easier. Now researchers can use the 3-D technology to test these seashell designs and other shapes that are even more complicated and may be even better to use for new structures.
Now try and answer these questions:
- Why are engineers trying to figure out how seashells work?
- What types of molluscs are the researchers studying? Why?
- How did the researchers go about studying the shells?
- What did they discover?
- How did they use the 3-D technology?
- Can you think of other things in nature that could be studied to help us create things that would be useful to humans?
To learn more about this research, you may want to check out the Popular Science article on it called Why Packaging and Fallout Shelters Should Take Design Cues from Seashells.
You can use this Science Update and its Related Resources to show your students how many scientists study the natural world to derive inspiration from it and to apply that knowledge in the design of materials for human purposes.
In addition, the Conversations with a Scientist: John Dabiri video features a biophysicist at the California Institute of Technology who studies jellyfish and blood flow to see what he can learn from them to better design submarines and wind farms.
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