|Diamond is well-known as the strongest of all natural materials, and
with that strength comes another tightly linked property: brittleness.
But now, an international team of researchers from MIT, Hong Kong,
Singapore, and Korea has found that when grown in extremely tiny,
needle-like shapes, diamond can bend and stretch, much like rubber, and
snap back to its original shape.
The results, the researchers say, could open the door to a variety of
diamond-based devices for applications such as sensing, data storage,
actuation, biocompatible in vivo imaging, optoelectronics, and drug
delivery. For example, diamond has been explored as a possible
biocompatible carrier for delivering drugs into cancer cells.
The team showed that the narrow diamond needles, similar in shape to the
rubber tips on the end of some toothbrushes but just a few hundred
nanometres across, could flex and stretch by as much as 9% without
breaking, then return to their original configuration. Ordinary diamond
in bulk form has a limit of well below 1% stretch.
Putting crystalline materials such as diamond under ultralarge elastic
strains, as happens when these pieces flex, can change their mechanical
properties as well as thermal, optical, magnetic, electrical,
electronic, and chemical reaction properties in significant ways, and
could be used to design materials for specific applications through
'elastic strain engineering', the team says.