“Flexoelectricity in ice electrification events”
FLEXOELECTRIC TRANSDUCTION
nature.com/articles/s41567-025-02995-6
https://phys.org/news/2025-09-scientists-ice-generates-electricity-bent.html
by Autonomous University of Barcelona, edited by Sadie Harley, reviewed by Robert Egan / September 1, 2025
“A study co-led by ICN2 reveals that ice is a flexoelectric material, meaning it can produce electricity when unevenly deformed. Published in Nature Physics, this discovery could have major technological implications while also shedding light on natural phenomena such as lightning. Frozen water is one of the most abundant substances on Earth. It is found in glaciers, on mountain peaks and in polar ice caps. Although it is a well-known material, studying its properties continues to yield fascinating results. An international study involving ICN2, at the UAB campus, Xi’an Jiaotong University (Xi’an) and Stony Brook University (New York), has shown for the first time that ordinary ice is a flexoelectric material. In other words, it can generate electricity when subjected to mechanical deformation. This discovery could have significant implications for the development of future technological devices and help to explain natural phenomena such as the formation of lightning in thunderstorms.
The study represents a significant step forward in our understanding of the electromechanical properties of ice. “We discovered that ice generates electric charge in response to mechanical stress at all temperatures. In addition, we identified a thin ‘ferroelectric’ layer at the surface at temperatures below -113ºC (160K),” explains Dr. Xin Wen, a member of the ICN2 Oxide Nanophysics Group and one of the study’s lead researchers. “This means that the ice surface can develop a natural electric polarization, which can be reversed when an external electric field is applied—similar to how the poles of a magnet can be flipped. The surface ferroelectricity is a cool discovery in its own right, as it means that ice may have not just one way to generate electricity, but two: ferroelectricity at very low temperatures, and flexoelectricity at higher temperatures all the way to 0 °C.” This property places ice on a par with electroceramic materials such as titanium dioxide, which are currently used in advanced technologies like sensors and capacitors.
“Experimental set-up for measuring ice flexoelectricity”
One of the most surprising aspects of this discovery is its connection to nature. The results of the study suggest that the flexoelectricity of ice could play a role in the electrification of clouds during thunderstorms, and therefore in the origin of lightning. It is known that lightning forms when an electric potential builds up in clouds due to collisions between ice particles, which become electrically charged. This potential is then released as a lightning strike. However, the mechanism by which ice particles become electrically charged has remained unclear, since ice is not piezoelectric—it cannot generate charge simply by being compressed during a collision. However, the study shows that ice can become electrically charged when it is subjected to inhomogeneous deformations, i.e. when it bends or deforms irregularly. “During our research, the electric potential generated by bending a slab of ice was measured.
Specifically, the block was placed between two metal plates and connected to a measuring device. The results match those previously observed in ice-particle collisions in thunderstorms,” explains ICREA Prof. Gustau Catalán, leader of the Oxide Nanophysics Group at ICN2. Thus, the results suggest that flexoelectricity could be one possible explanation for the generation of the electric potential that leads to lightning during storms. The researchers in the group are already exploring new lines of investigation aimed at exploiting these properties of ice for real-world applications. Although it is still a bit early to discuss potential solutions, 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.”
More information: X. Wen et al, Flexoelectricity and surface ferroelectricity of water ice, Nature Physics (2025). DOI: 10.1038/s41567-025-02995-6
ELECTRICITY LESSONS from ICE
https://arxiv.org/abs/2212.00323
https://earth.com/ordinary-ice-generates-electricity-when-bent-or-twisted
Ordinary ice generates electricity when bent or twisted
by Jordan Joseph / 09-03-2025
“Ice does not usually show up in conversations about electricity. A new study reports that ordinary frozen water generates electric charge when it bends, and the measured response is on the same order as benchmark electroceramics such as titanium dioxide and strontium titanate. The research also links this behavior to how storms build up charge, offering a fresh way to think about why lightning starts inside clouds. It adds a surface twist at extremely low temperatures that could matter in special environments.
Scientists call this effect flexo-electricity, the coupling between electric polarization and strain gradients in an insulator. A comprehensive review explains why any solid can show some flexoelectric response when it is bent unevenly or shaped with strong curvature. This is not the same as being piezoelectric, which requires a crystal structure that lacks inversion symmetry and creates charge directly under uniform compression or tension. Flexo-electricity does not need that symmetry break, so it can appear in materials that fail the piezoelectric test. Dr. Xin Wen of the Catalan Institute of Nanoscience and Nanotechnology (ICN2), located on the Universitat Autonoma de Barcelona campus, helped lead the experiments and modeling. The team combined precise bending tests with theory to tie the electrical signal to the mechanical shape of the ice.
The researchers shaped an ice slab, placed it between metal plates, then bent it in a controlled way while monitoring the voltage that appeared. The signal tracked how strongly the slab curved, which is exactly what flexo-electricity predicts. “We discovered that ice generates electric charge in response to mechanical stress at all temperatures,” said Dr. Wen. The tests showed that ice keeps producing a strong electrical signal across the whole range of temperatures where it stays solid, right up until it melts. That puts frozen water in the same league as some engineered materials, like certain oxides, that are commonly used in electronic sensors and capacitors. At extremely low temperatures, the researchers also noticed a very thin surface layer of ice that could flip its electrical orientation when an outside electric field was applied. This layer acts like a ferroelectric, but only on the surface and not throughout the entire block of ice.
Surface structure can dramatically change how ice interacts with its surroundings. In thunderclouds, tiny ice crystals crash into soft hailstones known as graupel, and those collisions shift electric charge from one particle to another. Studies in the lab and in real storms have shown that these encounters separate charge in ways that depend on temperature, building up the electric fields that allow lightning to form. Flexo-electricity offers an additional microphysical pathway for those particles to charge up during bouncy, irregular impacts that bend and twist their surfaces.
The new measurements match the scale of charge transfers inferred for real collisions, which helps knit lab physics to storm electrification without requiring piezoelectricity. A clear overview from NOAA outlines how separate charge regions form in a storm, build an electric field, and finally trigger a lightning discharge. The present work slides a mechanical bending effect into that picture, adding a way for collisions to do electrical work when particles deform unevenly. This matters most in the mixed phase region of a storm where supercooled droplets coat graupel and ice crystals ricochet through updrafts. Nonuniform stresses there are normal, so a bending driven mechanism is a natural candidate.
Ice is cheap to make, it molds into shapes easily, and it is abundant in cold places. Flexoelectric transduction could let engineers build simple sensors or pressure to voltage converters in situ, using water and metal contacts without high temperature processing or rare elements. Devices would not be limited to extreme cold, since the flexoelectric response persists up to the melting point. Designs would focus on geometry, because stronger curvature and sharper gradients usually drive larger signals in flexoelectric systems. The ferroelectric surface layer at about -171°F raises interesting options for switching behavior in deep cold. It could enable memory-like responses in polar regions or high altitude labs, where a modest electric field flips the surface polarization while the interior remains nonpolar.
Flexo-electricity turns uneven bending into electrical charge, even in a material long treated as electromechanically quiet under uniform pressure. Ice now joins the small set of everyday materials proven to convert mechanical shape changes into measurable voltage. In storm physics, it emerges as a credible new factor working alongside well-known non-inductive charging processes. Charge generated by bending fits naturally with the chaotic collisions of particles, linking lab findings to the electric dynamics of real clouds.
The study is published in the journal Nature Physics.”
GOLD from STRESSED QUARTZ
https://spectrevision.net/2024/09/04/gold-from-stressed-quartz/
FUNGAL ICE NUCLEATORS
https://spectrevision.net/2024/02/14/fungal-ice-nucleators/
EARTHQUAKE LIGHTS
https://spectrevision.net/2018/04/18/earthquake-lights/