Hong Kong researchers bent an ultrathin diamond membrane like paper and it unexpectedly started generating electricity by polarizing charge at its grain boundaries, overturning a century of scientific certainty about one of Earth’s most studied materials

Diamond has long been celebrated for almost every remarkable physical property a material can possess — hardness, thermal conductivity, chemical stability. Yet for more than a century, one thing it definitively could not do was generate electricity from mechanical force. That was settled science.

At the University of Hong Kong, researchers decided to push diamond to an unusual extreme: making it thin enough to bend. What happened when they flexed that membrane wasn’t supposed to be possible.

A rule that held for more than a century

Piezoelectricity is a straightforward phenomenon: bend or compress certain materials, and they generate a voltage. Press a crystal of quartz, and electrons shift. That electrical response powers everything from quartz watches to medical ultrasound probes. For over a hundred years, the rule was simple — mechanically deform diamond however you like, and you get no voltage. Nothing.

Diamond served as scaffolding — a passive structural support for other piezoelectric materials, never as an active electrical component in its own right.

That classification wasn’t a minor footnote. It directly shaped how engineers used diamond in microelectromechanical systems, or MEMS. Diamond served as scaffolding — a passive structural support for other piezoelectric materials, never as an active electrical component in its own right. Given that diamond excels at nearly everything else (extreme hardness, outstanding thermal conductivity, chemical stability, an ultrawide bandgap), the piezoelectric gap stood out as the one stubborn exception.

Making diamond thin enough to change its behavior

The HKU team’s key insight was that bulk diamond and ultrathin diamond aren’t the same material in any practical sense. Using a recently developed edge exfoliation method, they produced a polycrystalline diamond membrane thin enough to bend — something bulk diamond, famously brittle at scale, simply can’t do.

That flexibility was the experimental unlock. When the team deliberately flexed the membrane, stable voltage signals appeared. Detecting a signal, though, isn’t the same as proving piezoelectricity — surface contact and friction can produce electrical output through a separate mechanism called the triboelectric effect, essentially static electricity from rubbing surfaces. The researchers ran extensive mechanical cycling experiments under carefully controlled conditions, accounting for environmental interference. The voltage appeared consistently across cycles, and the evidence pointed clearly to the membrane itself.

Grain boundaries: the hidden source of the voltage

Understanding why the membrane generates electricity required digging into its internal structure. The distinction between polycrystalline and single-crystal diamond matters here. Single-crystal diamond is one continuous, uniform lattice. Polycrystalline diamond is made up of many tiny crystals packed together, and wherever two crystals meet, there’s a grain boundary.

First-principles calculations were used to model what happens at those boundaries during bending. The analysis revealed structural asymmetry: the grain boundaries aren’t geometrically uniform, and as the membrane flexes, electrical charge polarization builds up at those interfaces. That polarization creates a potential difference between the membrane’s upper and lower surfaces — and that difference is the voltage. Single-crystal diamond, lacking grain boundaries entirely, produces no such effect, which explains why researchers testing bulk or single-crystal samples had no reason to find piezoelectricity for over a century.

From lab curiosity to medical implants and micro energy systems

The practical implications follow naturally from diamond’s other properties. It’s biocompatible, chemically stable, and non-toxic — qualities that make it attractive for devices needing to function safely inside the human body over extended periods. A piezoelectric diamond membrane could, in principle, act as a self-powered sensor or a small energy source in an implantable medical device, harvesting mechanical energy from body movement or physiological pressure.

Beyond medicine, the finding points toward high-reliability micro energy systems and self-powered sensing technologies. Diamond’s durability under harsh conditions — temperature extremes, chemical exposure, radiation — gives it advantages that softer piezoelectric materials like polymers or ceramics can’t match. Those aren’t marginal differences; in demanding environments, they’re often decisive.

It’s worth being clear: this is early-stage research. The gap between a proof-of-concept membrane in a lab and a functional medical implant is substantial, and significant engineering work lies ahead. The proof-of-concept, at least, is now established.

The broader shift may be the most significant part of the story. For over a century, engineers designed around diamond’s electrical passivity. That constraint is now gone. A material already valued for what it could withstand turns out to also be capable of responding — of converting physical force into electrical signals. It’s worth pausing to consider how many other long-settled assumptions about well-studied materials might be waiting for someone to simply try a different shape.

The complete results are available here: Jixiang Jing et al. Uncovering piezoelectric effect in polycrystalline diamond membranes.Sci. Adv.12,eaea8318(2026). DOI:10.1126/sciadv.aea8318 

Daniel Garcia

Daniel García is an Editor-in-Chief with strong expertise in structural work and engineering principles. He combines this technical foundation with deep knowledge of energy, spatial design, and emerging technologies, bringing a forward-thinking and analytical approach to editorial leadership.