How to bend and stretch a diamond

DIAMONDS are among the strongest natural materials on earth, but scientists recently discovered it can actually bend when turned into ultrafine needle-like shapes.

A team of researchers from MIT and universities in Hong Kong, Singapore and Korea noted that when diamonds are transformed into “extremely tiny, needle-like shapes”, they stretch like rubber before transforming back to its original form.

The researchers said their findings present opportunities in a number of diamond-related processes such as sensing, data storage and drug delivery, among others.

“We developed a unique nanomechanical approach to precisely control and quantify the ultralarge elastic strain distributed in the nanodiamond samples,” said Yang Lu, co-author and an associate professor of mechanical and biomedical engineering at the Chinese University of Hong Kong.

The authors explained that a process called elastic strain engineering could alter the mechanical and reactive properties of diamond, allowing it to become flexible.

The process started by creating diamond needles through chemical vapour deposition. The resulting diamonds were etched to their final shape on a silicon surface. Afterward, the needle-like diamonds were pressed down and bent while researchers observed through a scanning electron microscope.

The experiment, followed by a number of simulations, is intended to measure the diamond’s tensile strength or the amount of strain it can handle before its breaking point.

“The controlled bending deformation also enables precise control and on-the-fly alterations of the maximum strain in the nano-needle below its fracture limit,” said Dao Ming, a co-author from MIT.

Using a computer model, the scientists measured that the maximum tensile strain of the needle was as high as 9 per cent.

“When elastic strains exceed 1 per cent, significant material property changes are expected through quantum mechanical calculations,” said Yonggang Huang, a professor of civil and environmental engineering and mechanical engineering at Northwestern University.

The study was published on April 20 in the journal Science.