Back to Ganoksin | FAQ | Contact

New use for an old material


#1

Hi all, I have just come across an article on Abalone shell that has
sparked my imagination. I would like to share my thoughts and I am
curious about any opinions that you folks may have on the subject. It
seems that Abalone shell is extremely strong and fracture resistant.
I know from past experience that it is very easy to carve using
diamond points (caution — as has been pointed out in past postings
care must be exercised with the dust of this material as it can be
hazardous to your health). How about using this material to carve
shallow wax molds. It seem to me that the durability, strength, and
fracture resistance of the Abalone in combination with the ease of
carving it would make this an ideal material to replace metal molds.

One concern I have about this is that I have seen old items (inlaid
furniture for example) that have inlayed shell in them, and the shell
appears to have shrunk. Does any one know anything about this and
what causes it, and is there any way to prevent it from happening.
Below you will find the article on Abalone that sparked this train of
thought as well as 2 postings from the forum dealing with Abalone’s
health hazards.

The postings (2 postings, there may be more) re the health hazards of
Abalone may be found at
http://www.ganoksin.com/orchid/archive/9809/msg00249.htm
http://www.ganoksin.com/orchid/archive/9809/msg00227.htm

BG Vancouver Can.

Nature publishes secret of abalone shell strength

http://www.eurekalert.org/releases/ucsb-nps061899.html

Researchers have cracked the mystery of the abalone shell’s toughness
and fracture resistance, according to the June 24 issue of the
journal Nature.

It’s all in the stretch, according to the discovery made at the
University of California, Santa Barbara, by a team of physicists,
molecular biologists and chemists.

The discovery suggests a new kind of biological “rubber” and helps
explain the exceptional strength of the plywood-like structure of the
abalone shell.

“Now that we’ve elucidated some of nature’s secrets, we can begin to
mimic these design patterns,” said Bettye L. Smith, research
associate in the Department of Physics, and lead author, who is
working toward designing and synthesizing strong and tough fibers
based on nature’s design.

The abalone shell is roughly 3,000 times more fracture resistant than
a single crystal of calcium carbonate, the mineral that makes up most
of its bulk. The UC Santa Barbara experiments show that the mechanism
behind the fracture resistance is in the polymer adhesive that holds
the crystal tablets together.

The researchers were able to reveal the properties of the adhesive in
single-molecule pulling experiments using the Atomic Force Microscope
(AFM) to measure the elasticity and strength of individual protein
molecules. This work was done under the direction of Paul K. Hansma,
professor of physics, by his laboratory group. (Hansma is a major
developer of new techniques using the AFM.)

“By grabbing a single molecule and pulling on it as if it were a
rubber band, you can measure the strength of a single molecular
fiber,” said Smith.

“Using this technique they discovered that the tiny crystal plates of
mineral that make up the abalone shell are held together with many
molecules of a protein that have a truly enormous capacity to absorb
shock without breaking,” said Dan Morse, professor of molecular
genetics and biochemistry and chairman of the Marine Biotechnology
Center.

“From studies in our lab in which we cloned the gene that codes for
this protein, we’re able to see a unique ‘modular’ structure that
makes the protein look like a series of springs or shock absorbers
linked together,” said Morse.

The experiments revealed that these springs are uncoiled when the
molecule is stressed, letting go one at a time, said Smith.
“Remarkably, when the stress is relaxed, they coil back, recovering
their original structure.”

These “sacrificial” links break in response to stress before the
whole molecule breaks, thus protecting the whole molecule. And these
"sacrificial" links can reform when the stress is gone, explained
Hansma.

Fibers produced synthetically are either very strong like Kevlar -
used in bulletproof vests - or tough and elastic like silicon rubber,
but very few combine both properties.

“These findings are nature’s secret of how to build fibers that are
simultaneously strong and elastically tough at the same time,” said
Smith. “We hope that by applying the secret to the synthesis of new
materials, that we’ll be able to produce inexpensive fibers that are
tailored to tough and strong high performance applications.”

Possible applications of such fibers include usage in textiles,
ropes, construction materials, aeronautics, camping gear, and
biomedical applications such as implant materials and prosthetics.