For over a 100 years, diamonds were considered incapable of producing electricity — one new experiment in Hong Kong has changed that

For more than a century, diamond has been prized for what it can withstand — not for its ability to produce electricity. That assumption may now need to change.

Scientists at the University of Hong Kong (HKU) have discovered that extremely thin and flexible diamond membranes can generate an electrical response when they are mechanically deformed. The finding challenges the long-held view that diamond cannot produce electricity through the piezoelectric effect.

The breakthrough could eventually lead to new types of self-powered sensors, miniature energy systems and medical implants that generate electrical signals from movement or deformation.

A material known for strength shows an unexpected weakness — and strength

Diamond is famous for being exceptionally hard, chemically stable and highly resistant to extreme conditions. It also has excellent thermal conductivity, a high acoustic velocity, strong dielectric properties and an ultrawide bandgap.

Those characteristics have made diamond attractive for advanced electronics and microelectromechanical systems, or MEMS.

But there was a major limitation.

Diamond has traditionally been regarded as non-piezoelectric. Unlike materials such as quartz and certain ceramics, it was not expected to develop an electrical voltage when squeezed, stretched or bent.

According to the HKU research team, that assumption has influenced how diamond has been incorporated into electronic devices for decades.

The new experiments suggest that the picture becomes very different when diamond is made extraordinarily thin.

Scientists found a way to make rigid diamond bend

The key to the discovery was not simply the diamond itself, but its form.

Researchers led by Professor Zhiqin Chu of HKU's Department of Electrical and Computer Engineering and Professor Yuan Lin of the Department of Mechanical Engineering developed ultrathin flexible membranes made from polycrystalline diamond.

Bulk diamond is famously difficult to deform. But when the material is reduced to a membrane only a tiny fraction of its usual thickness, it can flex under mechanical stress.

That gave the researchers a way to test whether deformation could trigger an electrical response that is not readily observable in ordinary diamond.

When the membranes were bent, the team detected voltage signals.

The researchers then repeatedly subjected the membranes to controlled mechanical cycles. The electrical response remained detectable, suggesting that the phenomenon was not simply a one-time effect or an experimental anomaly.

The researchers had to rule out other sources of electricity

Detecting a voltage was only the first step.

Mechanical experiments can produce electrical signals for several reasons, including the triboelectric effect — the generation of charge when different surfaces come into contact or move against each other.

To determine whether the diamond itself was responsible, the HKU researchers carried out additional tests under controlled conditions and performed repeated mechanical measurements.

The signals continued to appear as the diamond membranes were flexed.

The consistency of the results provided evidence for a genuine piezoelectric response from the ultrathin diamond structure, according to the researchers.

That makes the finding particularly significant because it suggests diamond may have an electrical function that was previously overlooked.

Tiny imperfections may be responsible for the breakthrough

The researchers also investigated what could cause a material traditionally considered non-piezoelectric to produce voltage.

Their calculations point toward the microscopic structure of the material.

The membranes are polycrystalline, meaning they contain numerous tiny diamond crystals. The boundaries where those crystals meet — known as grain boundaries — do not have perfectly symmetrical structures.

According to the team's first-principles calculations, mechanical bending can cause electrical polarization to develop around these boundaries.

As the membrane flexes, this polarization creates an electrical potential difference between its two surfaces.

In other words, the unusual electrical behaviour may not come from perfectly ordered diamond crystals themselves. Instead, the microscopic boundaries between crystals appear to play an important role.

Diamond could become more than just a passive component

The potential applications are what make the discovery especially intriguing.

Diamond already offers qualities that are difficult to combine in conventional electronic materials. It is exceptionally durable, chemically stable and considered highly biocompatible.

If its newly demonstrated piezoelectric behaviour can be engineered reliably, diamond membranes could potentially serve as both structural and electrically active components in miniature devices.

One possibility is sensing.

A flexible diamond membrane could generate an electrical signal when it bends or experiences mechanical stress, allowing the material to act as a sensor without necessarily requiring a separate power source.

Could diamond help power medical implants?

Medical technology could be another area where the discovery eventually proves useful.

The HKU researchers point to diamond's biocompatibility and chemical stability as characteristics that could make the material attractive for implantable technologies.

Future devices could potentially harvest small amounts of mechanical energy generated by movement inside the body. That energy could then be used to support extremely low-power sensors or other miniature electronics.

Such applications remain a future possibility rather than an established medical technology, but the underlying discovery provides researchers with a new direction to explore.

A new possibility for self-powered electronics

The broader significance of the research goes beyond diamond.

Modern electronic systems increasingly need sensors that can operate for long periods without conventional batteries. In extremely small devices, replacing or recharging a battery can be difficult, particularly when the device is implanted, sealed or placed in an inaccessible location.

Materials that can convert mechanical movement into electrical signals offer one potential solution.

The newly observed piezoelectric response in ultrathin diamond could therefore be relevant to the development of self-powered sensing systems and miniature energy harvesters.

Diamond's ability to operate in demanding environments could make it particularly interesting for applications where conventional materials may degrade or fail.

The discovery changes how scientists may look at diamond

The HKU study does not mean that ordinary diamonds can suddenly be used as household power generators.

The effect was observed in specially engineered, ultrathin polycrystalline diamond membranes under mechanical deformation. Turning that laboratory result into a practical energy technology will require further research into factors such as output, efficiency, scalability and device integration.

But the scientific shift is nevertheless striking.

A material long regarded as electrically inactive in this particular respect has demonstrated a repeatable response when its structure and dimensions are changed.

The discovery shows how dramatically material behaviour can change at very small scales — and suggests that even one of the best-understood natural materials may still contain technological surprises.

For researchers developing next-generation sensors and microscopic energy systems, that could make diamond worth looking at in an entirely new way.