Hong Kong – In a world’s first, an international research team led by City University of Hong Kong (CityU) has discovered that diamonds at nanoscale can undergo ultra-large, fully reversible elastic deformation. These findings can have a profound impact on the nanotechnology and biomedical fields, and even quantum information technologies.
Led by Dr Lu Yang, Associate Professor in the Department of Mechanical and Biomedical Engineering (MBE) at CityU, the research team demonstrated that when a diamond was downsized to nearly 100 nanometres in diameter, about one six-hundredth the size of human hair, up to around 9 percent of tensile elastic strain was recorded for single crystalline samples.
This figure is close to the maximum theoretically achievable strain for an ideal diamond crystal. In contrast, bulk diamond is usually regarded as “undeformable”, with only 0.1 to 0.35 percent strain recorded in the past.
This groundbreaking discovery was published in Science this month under the title “Ultralarge elastic deformation of nanoscale diamond”. The research team comprises of materials scientists and mechanical engineers from Massachusetts Institute of Technology, Ulsan National Institute of Science and Technology and the Nanyang Technological University.
In this project, Dr Lu and his team characterised the mechanical properties of nanoscale diamonds using their unique in situ nanoindenter platform inside electron microscopes. The diamond samples were fabricated by Professor Zhang Wenjun of CityU’s Department of Materials Science and Engineering.
Diamond, the hardest natural material, is used for cutting and drilling tools and to test other materials’ mechanical properties. To tackle the predicament of “diamond against diamond”, Dr Lu developed the novel “push to bend” test to exert force onto the diamond nanoneedle from the slant surface of a nanoindenter tip. Since the large deformation observed is fully reversible in nature, the diamond material retains the ability to instantaneously revert back to its original shape when the force causing the deformation is withdrawn. This means diamond can be elastic.
“This finding could fundamentally change our common understanding of diamond,” Dr Lu said. Because diamond is compatible with the human body, a possible area for future exploration is diamond needle-based drug delivery to human cells.
“Our discovery on nano diamond’s elasticity can help to make such intracellular delivery to be more durable, and cost-effective, noting that diamond needles are not as brittle as what we perceived,” Dr Lu explained.
“The next generation of information technology could also be based on diamond. Nanoscale diamonds with well controlled point defects can be used for quantum computing and quantum information processing,” said Dr Lu.
This discovery can help manufacturers produce highly reliable and efficient diamond resonators and sensors for faster data storage and transfer, Dr Lu predicted. Further, it can also pave the way for diamond’s practical applications in nanomechanical engineering, biomedical engineering, photonics, optoelectronics, and ultra-strength materials.