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Researchers at The University of Manchester have made an unexpected discovery about one of the world's most familiar substances—water. When confined to spaces a few atoms thick, water transforms into something completely unfamiliar, exhibiting properties more commonly associated with advanced materials like ferroelectrics and superionic liquids.

This surprising finding also contradicts what scientists previously knew about strongly confined water. Earlier work showed that confined water loses its ability to respond to an electric field, becoming "electrically dead" when measured in the direction perpendicular to surfaces. The new study reveals the complete opposite in the parallel direction—water's electrical response rises dramatically, by an order of magnitude.

The study, in Nature by a team led by Dr. Laura Fumagalli in collaboration with Prof. Andre Geim, used an advanced technique called scanning dielectric microscopy to peer into water's electrical secrets at the true nanoscale. They trapped water in channels so narrow they held only a handful of molecular layers.

The results are striking: bulk water has a dielectric constant around 80, but when thinned to just 1–2 nanometers, its in-plane dielectric constant reaches values close to 1,000—on par with ferroelectrics used in advanced electronics. At the same time, water's conductivity increases to values approaching those of superionic liquids, materials considered highly promising for next-generation batteries.

"Think of it as if water has a split personality," explains Dr. Fumagalli. "In one direction, it is electrically dead, but look at it in profile and suddenly it becomes electrically super-active. Nobody expected such dramatic behavior."

The discovery required the team to develop ultrasensitive measurement techniques capable of probing water layers much thinner than the skin of a virus and track their electrical response across frequencies from kilohertz to gigahertz—spanning six orders of magnitude.

The research also reveals that confined water exists in two distinct electrical regimes. For channels larger than several nanometers, water behaves like its bulk form, albeit with much higher conductivity. But once squeezed to atomic dimensions, it undergoes a sharp transition into a new "superionic-like" state.

This transformation occurs because extreme confinement disrupts water's hydrogen-bond network, which in bulk is a dynamic but rather ordered structure. At the molecular scale, this network becomes disordered, allowing dipoles to align more easily with electric fields and enabling rapid proton transport.

"Just as graphene revealed unexpected physics when graphite was thinned down to a single atomic layer, this research shows that even water—the most studied liquid on Earth—can still surprise us when squeezed to its absolute thinnest," notes Prof. Geim, who previously won the Nobel Prize for graphene research.

The implications extend far beyond fundamental science. Insights into water's electrical properties at the nanoscale are crucial not only for physics and chemistry but also for technologies ranging from advanced batteries and microfluidics to nanoscale electronics and biology.

"Our study changes how we should think about water," adds Dr. Fumagalli. "The most ordinary substance on Earth has extraordinary talents that were hidden until now."