In storm clouds, ice does more than just float or fall—it might actually help generate electricity. A new study in Nature Physics finds that when ordinary ice is bent, it can produce an electric charge.

Researchers from the Catalan Institute of Nanoscience and Nanotechnology (ICN2), Xi’an Jiaotong University, and Stony Brook University have shown that ice is flexoelectric. In other words, it can generate an electric charge when subjected to uneven mechanical stress such as bending or twisting. This once-overlooked property could illuminate how lightning forms and even inspire new ice-based technologies in the coldest places on Earth.

“We discovered that ice generates electric charge in response to mechanical stress at all temperatures,” said Dr. Xin Wen, lead author and nanophysicist at ICN2.

The Shocking Behavior of Ordinary Ice

Most people are familiar with piezoelectricity, where materials like quartz or certain ceramics emit electric charge under compression. But ice Ih (the common form found in glaciers and freezers) is not piezoelectric. This is due to how water molecules line up in its crystal structure: even though each molecule is polar, the collective pattern cancels the overall effect.

“Despite the polarity of individual water molecules, common ice Ih is not piezoelectric, due to the geometric frustration introduced by the so-called Bernal–Fowler rules,” the research team explains in their paper.

But there’s a twist—literally. If you bend the material, you’re no longer dealing with uniform stress. Instead, one side gets compressed, the other stretched. This uneven stress gradient can polarize the material through a phenomenon called flexoelectricity. Unlike piezoelectricity, flexoelectricity doesn’t require the atoms to be neatly aligned, and it can occur in any material, including ice.

To test this, the team created “ice capacitors”—thin slabs of pure ice sandwiched between metal electrodes—and then bent them using a precise three-point mechanical rig. They observed measurable electric charges appear at all temperatures tested, from a bone-chilling –130 °C up to the melting point of ice.

“The results match those previously observed in ice-particle collisions in thunderstorms,” said ICREA Professor Gustau Catalán, leader of the Oxide Nanophysics Group at ICN2.

Two Electric Faces of Ice

Flexoelectricity wasn’t the only surprise hiding in the frozen slabs. When the researchers cooled the ice below –113 °C (160 K), they noticed something unusual: a spike in the material’s electric response.

That anomaly turned out to be a surface ferroelectric phase—a previously unknown state where the outermost nanometers of the ice became ferroelectric. That means they could hold a stable electric polarization that flips when an external electric field is applied, much like the magnetic poles of a magnet.

“This means that the ice surface can develop a natural electric polarization, which can be reversed when an external electric field is applied,” explained Dr. Wen.

In short, ice appears to have two different ways to generate electricity:

• At temperatures below –113 °C, the surface layer becomes ferroelectric.
• From –113 °C up to 0 °C, the entire slab can produce charge via flexoelectricity.

Solving a Thunderous Mystery

This finding could end up solving another conundrum. For decades, scientists have puzzled over one of weather’s great mysteries: how does lightning form inside clouds?

It’s well known that collisions between rising ice crystals and falling graupel (soft hail) particles build up charge separation in storm clouds. But ice isn’t piezoelectric—so where does the charge come from?

This new study offers a possible answer. When those particles crash into each other, they bend, dent, and deform. The resulting strain gradients could trigger flexoelectric polarization, generating electric fields and attracting charges to the collision site. When the particles part ways, one keeps more electrons, the other less, resulting in charge separation.

“The calculated flexoelectric polarization during a typical ice–graupel collision reaches ~10⁻⁴ C/m² on the graupel surface,” the authors wrote.

This is enough, they argue, to account for the amount of charge measured in past laboratory experiments on storm cloud electrification. Moreover, the direction of the charge flip even changes with temperature—matching observed polarity reversals in actual thunderstorms.

Still, the researchers caution that this is not the full story. The real world is messy. Other mechanisms like fracturing, friction, or impurity diffusion may still contribute. But the evidence now suggests that flexoelectricity is at least part of the lightning equation.

Can Ice Power Future Technologies?

Beyond weather, the findings may spark innovations in future engineering.

The strength of the ice’s flexoelectric effect is on par with titanium dioxide and strontium titanate, two ceramic materials used in capacitors and sensors. That opens the possibility of using ice itself as an active component in low-cost, temporary electronics that function in arctic or high-altitude environments.

“This discovery could pave the way for the development of new electronic devices that use ice as an active material, which could be fabricated directly in cold environments,” said Prof. Catalán.

Whether that means sensors embedded in polar glaciers, or energy-harvesting surfaces on frozen satellites, is still speculative. But the principle is now there: when ice gets stressed, it responds—with a spark.