Nanoscale View Finally Reveals What Makes 'Nacre' Shell Material So Resilient

Nacre is an extremely resilient biomaterial found in the shells of mollusks that has perplexed scientists and engineers for decades. It's been known that the material is made of microscopic “bricks” of the mineral aragonite and laced together with a “mortar” made of organic material; now, new visual evidence captured by University of Michigan researchers reveals the exact mechanisms that give nacre its resiliency. Using tiny piezo-electric micro-indenters, the team was able to exert force on the shells while under an electron microscope and watch what happened in real time. In research published in Nature Communications , the researchers explain that the “bricks” are actually multi-sided tablets only a few hundred nanometers in size. Ordinarily, these tablets remain separate, arranged in layers and cushioned by a thin layer of organic “mortar.” But when stress is applied to the shells, the “mortar” squishes aside and the tablets lock together, forming what is essentially a solid surface. When the force is removed, the structure springs back, without losing any strength or resilience.