Diamonds are hard, yet very brittle. So if you try to flex or stretch something that’s brittle, the result is obvious – you would shatter it quite easily. But what if I say – diamonds can flex and stretch, much like rubber without breaking? That’s what a team of researchers from MIT, Hong Kong, Singapore, and Korea has discovered.
Diamonds are strong because its molecular structure consists of five carbon atoms, and each atom shares an electron with each other in a tetrahedral lattice. The bonds between these carbon atoms are extremely strong and require a lot of energy to break because of this tetrahedral arrangement.
Diamonds, because of their property, have a wide range of applications in industries – grinding, drilling, cutting and polishing to name a few. But will this new discovery that it can bend and stretch have any potential applications? The answer is yes, and researchers say it can be used in a variety of diamond-based devices for applications in technology such as sensing, data storage, actuation, biocompatible in vivo imaging, and optoelectronic. Well, scientists have reconnoitered diamonds as a possible biocompatible carrier for delivering drugs into cancer cells.
According to the paper published in the journal Science, senior author Ming Dao and his team grew the diamond into extremely tiny, needle-like shapes(a few hundred nanometers across) through a chemical vapor deposition process, and then engraved to their final shape. And as they pressed down on the needles with a standard nanoindenter diamond tip while observing them in a scanning electron microscope, they found that the narrow diamond needles, could flex and stretch by as much as 9 percent without any breakage, then snap back to their original shape – much like the rubber.
MIT postdoc Daniel Bernoulli, also involved in the study, described that ordinary diamond in bulk form has a limit of well below 1 percent stretch, but he was surprised with the outcome.
“We developed a unique nanomechanical approach to precisely control and quantify the ultralarge elastic strain distributed in the nanodiamond samples,” explains Yang Lu, senior co-author and associate professor of mechanical and biomedical engineering at CUHK in a news release.
“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.
In order to understand and accurately determine the stress and strain the diamonds needles could handle without breaking, the team also developed a computer model of the nonlinear elastic deformation for the actual geometry of the diamond needle. The model predicted that the tensile strength of the nanoscale diamond was close to “the theoretical limit achievable by defect-free diamond,” and its tensile strain was as high as 9 percent.
Failure occurred when the tensile strain reached 9 percent, for the diamond needle carved out of a single crystal. But if the needle was made of many grains of diamond, it could handle unusually large strains, the researchers noted.