Abalone Shell - strength through clever design
by TreeHugger on 03.29.05
The abalone - yet another marine organism with incredible materials engineering know how (see Man vs Mussel). A recent news article in the New York Times featured the abalone and how Dr. Kenneth Vecchio of the University of California San Diego created an aluminum and titanium mixture which mimicked the clever design of the abalone shell. The design is the key reason to why the abalone shell is so tough. It is the design which makes the shell almost 3,000 times stronger then the materials it is made out of alone; chalk (calcium carbonate) and protein. Drop an abalone shell from my second story window and it will not break, but drop chalk and watch it shatter (the local kids had a great time drawing on the sidewalk with it too- reuse!). I guess if you dropped protein, say an egg without the shell it wouldn’t really hold together well either – you see my point here, design is key, something we here at TH have been saying for a while. Take a look at the design on the molecular level (more photos in extension)
As you can see in the picture the abalone lays down layer upon layer of the calcium carbonate material between sheets of protein (which is a little bit harder to see-but they assure me it is there). Looks a little like plywood, but by creating this organization at the microscopic scale, it increases its toughness and makes for an amazing material. The bar down in the lower right corner is 1 micro-meter or about 100 times smaller then a human hair. But the amazing engineering doesn’t stop there, the abalone takes it all the way to the atomic level, and actually chooses the crystal formation it ‘wants’ for the calcium carbonate, the material is a mineral with a specific crystal structure called Aragonite. While the abalone can do this with calcium carbonate every day of the week, we have yet to be able to control production so easily, without expensive chemicals, processes, and heating which make the product unreasonably expensive for any application. Professor Daniel Morse and his lab from the University of California Santa Barbara have been investigating the proteins involved in creating the unique structure, with the hope that we may be able to reproduce these feats on the molecular level, without using expensive or damaging processes.
Here is the picture of the titanium alloy “shell” that had a tungsten rod fired into it at 2,000 mph. The sheet in the picture is only ¾ of an inch thick. While the material is not exactly at the scale of the abalone, it is a good example of how important design is to engineering, and how biology has a large number of designs and environmentally sound processes waiting for us to discover.
The field of abalone research has developed into a rather large and international group of materials engineers and biologists. From the Biomolecular Materials Group headed by Angela Belcher at MIT, to
Marcela Bilek studying materials coating and surfaces at the University of Sydney, biomimetics can offer solutions to problems we may not have even known we have. :: [by T. McGee]
