Play store
Researchers at the University of Hong Kong (HKU) have discovered that ultrathin diamond can generate electricity when mechanically deformed, challenging a scientific understanding that has stood for more than a century.
The study was led by Professor Zhiqin Chu, associate professor in the Department of Electrical and Computer Engineering, and Professor Yuan Lin, professor in the Department of Mechanical Engineering at HKU’s Faculty of Engineering.
Since the early 1900s, diamond has generally been regarded as a non-piezoelectric material, meaning it was not expected to produce an electrical voltage when subjected to mechanical stress.
The finding could expand the use of diamond beyond its traditional role as a highly durable structural material in microelectromechanical systems (MEMS).
Despite its exceptional hardness, strength, chemical stability, thermal conductivity, acoustic velocity, dielectric breakdown strength and ultrawide bandgap, diamond has generally been used to support other piezoelectric materials rather than generate electrical signals itself.
To investigate whether diamond could exhibit piezoelectric behaviour under extreme mechanical conditions, the HKU team used an edge exfoliation technique to produce an ultrathin, flexible polycrystalline diamond membrane.
When the membrane was deliberately bent, researchers detected stable voltage signals. They conducted extensive mechanical cycling tests under controlled conditions to verify the results and rule out environmental interference and triboelectric effects caused by surface contact or friction.
The electrical signals appeared consistently and repeatedly, providing evidence that the diamond membrane itself was producing a piezoelectric response.
First-principles calculations suggested that the effect originates from asymmetry at grain boundaries within the polycrystalline diamond. As the membrane bends, charge polarization develops around these boundaries, creating a potential difference between its upper and lower surfaces and generating voltage.
The discovery could have applications in medical devices and miniature energy systems. Diamond is biocompatible, chemically stable and non-toxic, making piezoelectric diamond membranes potentially suitable for implantable medical devices, self-powered sensors and systems that detect bending or deformation.
The researchers said the findings could pave the way for high-reliability micro-energy systems and self-powered sensing technologies, giving diamond an active electrical function rather than limiting it to a passive structural role.