Dynamist Blog

Better (Replacement) Bones

Gretchen Cuda of Wired News reports that researchers at Lawrence Berkeley Labs have found an ingenious way to mimic some of nature's strongest structures, promising better artificial joints.

A team of researchers in the Materials Science Division at Lawrence Berkeley National Laboratory has managed to imitate the complex structures found in ice and mollusk shells, and the ultra-strong material could lead to everything from stronger artificial bone to airplane parts.

The scientists used the physics of ice formation to develop ceramic composites four times stronger than current technology. "Because we can control the freezing of ice we could get very sophisticated structures," says Eduardo Saiz, a physicist at Lawrence Berkeley and one of the authors on a paper published in January in Science....

Ceramic has been the material of choice in joint-replacement surgeries for years because it lasts longer and produces fewer immune reactions than metal or plastic. It also contain millions of tiny pores that the patient's own bone cells can bind to, strengthening the new joint. But the spongelike structure of conventional ceramic is weak, and can fracture....

The breakthrough came after the Berkeley team realized that similar layered structures formed when mineral-rich water froze. So they tried freezing a mixture of water and hydroxyapotite, the mineral component of bone. As the ice formed, the minerals became trapped between the layers of ice crystals. They freeze-dried the material to remove the ice, leaving behind hydroxyapotite layers similar to nacre's. By increasing the speed of the freezing process, they could decrease the layers' thickness to just 1 micron -- nearly reproducing the scale found in nature.

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