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, published in the journal Nature Physics, 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). 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 " explains Dr Xin Wen, a member of the ICN2 Oxide Nanophysics Group and one of the study's lead researchers. 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.
Ice, flexoelectricity and thunderstorms
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.
Future perspectives
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.
Reference:
Wen, X; Ma, Q; Mannino, A; Fernandez-Serra, M; Shen, S; Catalan, G. Flexoelectricity and surface ferroelectricity of water ice. Nature Physics. (2025).
