HKU scientists discover ultrathin diamond membranes generate electricity

August 31, 2026 at 05:00 AM2 min

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Researchers at the University of Hong Kong have discovered that ultrathin, flexible diamond membranes produce a measurable piezoelectric response. The finding challenges a century-old assumption that diamond is non-piezoelectric. The team observed stable voltage signals when flexing the membranes, with the effect attributed to grain boundary asymmetry.

Key Facts

The University of Hong Kong team led by Professor Zhiqin Chu and Professor Yuan Lin produced ultrathin polycrystalline diamond membranes using an edge exfoliation method.
Flexing the diamond membranes generated stable voltage signals, confirmed through extensive mechanical cycling experiments that ruled out environmental interference and triboelectric effects.
First-principles calculations indicate that charge polarization builds up around grain boundaries in the polycrystalline diamond as the membrane bends, creating a potential difference between the upper and lower surfaces.
Diamond has been classified as non-piezoelectric since the early 1900s, limiting its use in microelectromechanical systems to structural support for other piezoelectric materials.

Piezoelectric Response Discovery

Researchers at the University of Hong Kong have demonstrated that ultrathin, highly flexible diamond membranes can produce a measurable piezoelectric response. The work was led by Professor Zhiqin Chu of the Department of Electrical and Computer Engineering and Professor Yuan Lin of the Department of Mechanical Engineering. The team used a recently developed edge exfoliation method to create ultrathin, flexible polycrystalline diamond membranes. When the researchers deliberately flexed the membrane, they observed stable voltage signals.

Mechanism and Validation

Extensive mechanical cycling experiments under controlled conditions ruled out environmental interference and triboelectric effects. The voltage appeared consistently and repeatedly, providing strong evidence that the diamond membrane itself was producing a piezoelectric response. First-principles calculations point to asymmetry at the grain boundaries inside the polycrystalline diamond membrane as the source of the effect. As the membrane bends more strongly, electrical charge polarization builds up around those grain boundaries, creating a difference in electrical potential between the upper and lower surfaces.

Implications for Diamond Applications

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. Despite its exceptional hardness, strength, chemical stability, high acoustic velocity, thermal conductivity, dielectric breakdown strength and ultrawide bandgap, diamond has typically served only as a structural support for other piezoelectric materials in microelectromechanical systems. The discovery could open new possibilities for diamond in areas where durability and safety are especially important.