Researchers from MIT, Hong Kong, Singapore and Korea have discovered that when diamonds are grown in extremely tiny, needle-like shapes, they can be pulled and stretched and snap back to their original shape.
Ordinary diamonds can only withstand stresses of well below 1% without breaking, but needle nanodiamonds can stretch by as much as 9%.
“It was very surprising to see the amount of elastic deformation the nanoscale diamond could sustain,” said MIT postdoc Daniel Bernoulli in a statement.
This discovery is not going to give us bendy jewellery though, its applications are far more interesting than that. Needle nanodiamonds could be used in a variety of devices for sensing or data storage. They could also be biocompatible for vivo imaging, optoelectronics or even delivering drugs into cancer cells.
When crystalline materials like diamond are flexed, it changes their mechanical properties as well as thermal, optical, magnetic, electrical, electronic and chemical properties. A process known as elastic strain engineering could be used to design nanodiamond materials for a variety of applications, taking advantage of these properties.
The team used a chemical vapor deposit process to grow the diamonds and then etched them into their needle shape – a bit like the bristles of a toothbrush but much, much smaller. Then they pressed down on their creations with a standard nanoindenter diamond tip to see how much they could take.
Follow-up computer simulations determined the precise amount of stress the nanodiamonds could take and also determined that the corresponding maximum local stress was close to the known ideal tensile strength of diamond – the theoretical limit achievable with a perfect, defect-free diamond.
“The surprise finding of ultralarge elastic deformation in a hard and brittle material — diamond — opens up unprecedented possibilities for tuning its optical, optomechanical, magnetic, phononic, and catalytic properties through elastic strain engineering,” said Yonggang Huang, a professor of civil and environmental engineering and mechanical engineering at Northwestern University, who was not involved in this research.
“When elastic strains exceed 1%, significant material property changes are expected through quantum mechanical calculations. With controlled elastic strains between 0 to 9% in diamond, we expect to see some surprising property changes.”
The research was published in Science magazine.
Brid-Aine Parnell, CONTRIBUTOR