Researchers at the University of Hong Kong (HKU) have discovered that ultrathin, highly flexible diamond membranes can produce a measurable piezoelectric response, challenging a scientific assumption that has stood for more than a century.
Since the early 1900s, diamond has generally been classified as a non-piezoelectric material — meaning it was not expected to generate an electrical voltage when mechanically deformed. That limitation has shaped how diamond has been used in engineering, limiting it to a structural role despite its exceptional hardness, thermal conductivity, and chemical stability.
To test whether diamond could behave differently under extreme mechanical conditions, the HKU team used a recently developed edge exfoliation method to produce ultrathin, flexible polycrystalline diamond membranes. When the researchers deliberately flexed the membrane, they observed stable voltage signals.
Extensive mechanical cycling experiments under controlled conditions confirmed the electrical output was genuine, ruling out environmental interference and triboelectric effects. The voltage appeared consistently and repeatedly, providing strong evidence of a true piezoelectric response.
First-principles calculations revealed why the effect occurs: asymmetry at grain boundaries inside the polycrystalline diamond membrane. As the membrane bends, electrical charge polarization builds up around those boundaries, creating a potential difference between the upper and lower surfaces.
The discovery could open new possibilities for diamond in medical and energy technologies. Diamond is highly biocompatible, chemically stable, and non-toxic, making it attractive for implantable medical devices as self-generating power sources or sensors that detect bending and deformation.
The findings, published in Science Advances, introduce a fundamentally new way to give diamond active electrical functionality rather than using it only as a passive structural material.
