The lightweight skeletons of organisms such as sea sponges
display a strength that far exceeds that of manmade products constructed from
similar materials. Scientists have long suspected that the difference has to do
with the hierarchical architecture of the biological materials—the way the
silica-based skeletons are built up from different structural elements, some of
which are measured on the scale of billionths of meters, or nanometers. Now
engineers at the California Institute of Technology (Caltech) have mimicked
such a structure by creating nanostructured, hollow ceramic scaffolds, and have
found that the small building blocks, or unit cells, do indeed display
remarkable strength and resistance to failure despite being more than 85
percent air.