Scientists find way to bend, stretch diamond

In a first, scientists have found that diamond can bend and stretch much like rubber, and snap back to its original form when grown in extremely tiny, needle-like shapes.

Diamond is well-known as the strongest of all natural materials, and with that strength comes another tightly linked property: brittleness.

The finding by researchers at Massachusetts Institute of Technology (MIT) in the US 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.

Published in the journal Science, the research shows that the narrow diamond needles, similar in shape to the rubber tips on the end of some toothbrushes but just a few hundred nanometers across, could flex and stretch by as much as nine per cent without breaking, then return to their original configuration.

Ordinary diamond in bulk form, and has a limit of well below one per cent stretch, said MIT postdoc Daniel Bernoulli.

"It was very surprising to see the amount of elastic deformation the nanoscale diamond could sustain," he said.

"We developed a unique nanomechanical approach to precisely control and quantify the ultralarge elastic strain distributed in the nanodiamond samples," said Yang Lu, associate professor at Chinese University of Hong Kong (CUHK).

Putting crystalline materials such as diamond under ultralarge elastic strains can change their mechanical properties as well as thermal, optical, magnetic, electrical, electronic, and chemical reaction properties in significant way, researchers said.

This could be used to design materials for specific applications through "elastic strain engineering," they said.

The team measured the bending of the diamond needles, which were grown through a chemical vapour deposition process and then etched to their final shape, by observing them in a scanning electron microscope while pressing down on the needles with a standard nanoindenter diamond tip (essentially the corner of a cube).

Following the experimental tests using this system, the team did many detailed simulations to interpret the results and was able to determine precisely how much stress and strain the diamond needles could accommodate without breaking.