Have you ever tried to smash open a mollusk shell? They’re pretty hard right? Actually the shells are one of the strongest, but lightest materials produced by Mother Nature. Now image what we could build if we could produce a synthetic version of the shells. Researchers at Lawrence Berkeley National Laboratory have managed to imitate the complex structures found in ice and mollusk shells. They created a ceramic composite that is four times stronger than current ceramics by using the physics behind ice formation. But what does that have to do with shells you say?
Mollusk shells are similar to bone and are comprised of thin layers of calcium carbonate interspersed with organic material. All of this is referred to as nacre and each layer is half a micron thick (that’s tiny). Nacre has been synthetically recreated in a lab, but it’s not easy, until now.
The team at Berkeley found that they could form these structures by freezing mineral rich water. They used a mixture of water and hydroxyapotite (mineral compound in bone). As the ice formed the minerals became trapped in the ice crystals and then they freeze dried it to remove the water, leaving behind a layer of hydroxyapotite. Increasing the speed of the freezing process decreased the layer’s thickness to one micron.
Ceramics are the substance of choice for joint-replacement because it produces fewer immune responses and lasts longer than plastics or metal. The problem with the current stuff is that it’s weak and can fracture. The new method produces a much stronger structure. But the possibilities don’t end there. Researchers envision many applications for the new ceramic from dental implants to airplane parts.