From mother of pearl to mother of invention
A sea shell on a roadside vendor’s table caught Mehmet Sarikaya’s eye during a family trip through the Olympic Peninsula more than 20 years ago.
The former home of a red abalone mollusk from the California coast, the shell was an unusual find near Washington waters. Here, abalone shells tend to be green. Sarikaya bought his roadside find for $20 and took it home for a closer look.
Sarikaya knew preparing a sample of the shell would not be easy. The high protein content and water trapped inside made the shell sensitive to the radiation that electron microscopes generate to capture detailed imagery.
Sarikaya had practice preparing samples of similarly sensitive materials such as ceramic superconductors, so he put his experience to work.
“This was the only way I could get a detailed view of the layered structure of calcium carbonate and the protein matter in-between,” Sarikaya said. “No one had ever prepared or even thought of preparing a transmission electron microscope sample from mother of pearl, which I realized later on.”
Sarikaya’s resulting study was a groundbreaking effort in the developing field of molecular biomimetics, which draws inspiration from nature to create materials with applications in engineering, medicine and more.
An abalone’s shell is made of tiny calcium carbonate tiles stacked like bricks. Between the layers of shell is an iridescent protein material called nacre, or mother of pearl.
When the shell is struck, the tiles slide instead of shattering and the mother of pearl flexes to absorb the blow. “Mother of pearl is one of the strongest laminated materials ever produced,” Sarikaya said.
The proteins in mother of pearl and other biological materials such as bone and antler are formed out of peptides, which are short polymer chains of amino acids. “Nature uses proteins to make all conceivable molecules and tissues in an organism,” Sarikaya said. “Every molecule inside of you is made from peptides or proteins.”
Using biology as a guide, molecular biomimeticists aim to control interactions between these peptides and other materials. Ultimately, they seek to use peptides as building blocks in the programmed formation of materials with medical and technological applications.
“Our approach is to learn and adapt biology’s ways to use peptides as molecular agents in synthesizing, assembling and forming complex materials and functional systems for technology and medicine,” Sarikaya said.
Sarikaya joined the MSE faculty in 1984. Early on, he and colleagues focused on how to create materials that mimicked the layered, nanocomposite architecture of materials such as abalone shell. In the mid-1990s, his focus shifted away from creating the materials in labs and toward discovering how organisms do it in nature.
“Under genetic control, proteins both collect and transport raw materials, and consistently and uniformly self- and co-assemble subunits into tissues and organs,” Sarikaya said. “Whether in controlling tissue formation, biological functions or physical performance, proteins are an indispensable part of biological structures and systems.”
Sarikaya directs the Genetically Engineered Materials Science and Engineering Center (GEMSEC). GEMSEC is an interdisciplinary team of scientists and engineers working together to marry biology, computational science, and materials science and engineering at the fundamental level. The center was established at UW in 2005 with a $7.7 million grant from the National Science Foundation.
In a department that began more than 100 years ago as the UW’s School of Mining, where does a field so heavily influenced by biology fit in? “Mining is getting minerals out of the ground, and using enrichment processes to separate useful minerals from the rest of the dirt,” Sarikaya said. “It turns out, this is exactly how organisms make materials using the raw ingredients in the dirt.”
UW Department of Materials Science & Engineering
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