The most common liquid on Earth has surprised scientists once again

Water looks familiar in a glass, yet it behaves very differently when pushed to extremes. When researchers in Manchester squeezed water into ultra-thin channels inside crystals, it carried electric current up to 100,000 times better than ordinary water.

This discovery is important because many of nature’s crucial processes occur in areas where water touches a surface, not deep in the liquid. 

Changing how easily charges move in those tiny regions could reshape how we understand chemistry inside cells and inside advanced materials.

Squeezed water molecules

In everyday conditions, water molecules hook together through a hydrogen bond network, a shifting web of weak attractions between neighboring molecules. 

This network helps water dissolve salts, stabilizes proteins, and already gives bulk water a surprisingly high ability to let electric charges move.

The work was led by Laura Fumagalli, a physicist at the University of Manchester who specializes in nanoscale measurements. 

Her research focuses on how water and other liquids behave when confined between atomically flat materials.

Many key reactions happen in interfacial water, the thin layer right where liquid water touches a solid surface. 

Inside cells, that layer lines membranes, proteins, and DNA, so any special behavior there can strongly influence life’s chemistry.

“Essentially, the water was electrically dead,” said Fumagalli, describing that controversial result. 

That layer had an out of plane dielectric constant, describing how strongly a material polarizes in an electric field, of about 2 in that study.

Nanochannels for flat water layers

They created narrow nanochannels, tiny rectangular passages about 0.00000008 inches tall in the thinnest devices, by stacking sheets of graphite and hexagonal boron nitride. 

Water was drawn into these slits from the side, forming perfectly flat layers hidden between the crystals.

A technique called scanning dielectric microscopy, which uses a tiny vibrating tip to sense local electrical response, lets them probe each channel. 

The tip responded to how easily charges in the water layer moved or rearranged when an alternating voltage was applied.

They swept the tip’s voltage from a few hundred cycles per second up to nearly a billion cycles per second. That range let them see how the water’s stored charge and flowing charge changed along each layer. 

“That is what we call strong confinement,” said Fumagalli. As the channels thin so much that the two interfaces start to overlap, the team refers to this regime as strong confinement. 

From quiet water to proton highways

At the tightest confinement, the in-plane dielectric constant reached roughly 1,000 and the conductivity reached several siemens per meter in the study.

Those values are comparable to some commercial proton conductors and start to overlap with materials known as superionic liquids.

For wider gaps, the water showed enhanced proton conductivity, meaning positively charged hydrogen ions moved more easily along the channel. 

As the gap narrowed step by step, that conductivity kept rising while the in-plane response still looked fairly similar to ordinary liquid water.

The dramatic peak appeared when the two interfacial layers touched, creating quasi-2D water, water arranged in four or five layers across the gap. 

In that configuration, the hydrogen bond pattern becomes highly disordered within each layer, which makes it easier for dipoles and protons to rearrange sideways.

Hydrogen bonds inside water layers

Breaking and reforming hydrogen bonds can also accelerate proton motion through the Grotthuss mechanism, where protons hop between neighboring water molecules in a relay. 

When confinement scrambles the hydrogen bond pattern within these layers, that relay becomes easier sideways along the channel, boosting how quickly charge moves.

Under extreme pressures and temperatures, water can enter superionic ice, a phase where oxygen atoms stay fixed while protons flow freely. 

Experiments using shock-compressed water have measured ionic conductivities above 100 siemens per centimeter in this state.

Commercial fuel cells rely on proton exchange membranes, thin films that let protons cross between electrodes but block electrons. 

In materials such as Nafion, measured proton conductivities span roughly 0.1 to 1.5 siemens per centimeter at room temperature in Nafion experiments.

Recent work shows that interfacial water forms ordered layers with hydrogen bonds unlike bulk liquid, in an overview of interfacial water properties. 

Those rearrangements can change diffusion, reaction rates, and even phase transitions at surfaces, so nanoconfined water’s wild electrical behavior fits into a larger pattern.

Lessons from squeezed water layers

Cell membranes and protein surfaces present countless nanoscale grooves and pockets where layered water could behave in this highly conductive way. 

If proton flow along those layers becomes easier, cells might route charges along specific paths more efficiently than models based on bulk water assume.

At surfaces, the electric double layer, a thin zone where ions crowd near a surface, controls how batteries and membranes work. 

The new picture of interfacial water, where electrical behavior depends on direction within molecular layers, suggests many electrochemical models need revision at nanometer scales.

Designers of membranes and energy devices could exploit such proton-rich layers to route signals and ions in ways bulk water never allowed. 

Because the Manchester experiments measure local properties instead of averaging over many pores, they offer a toolkit for testing other liquids under tight confinement.

For a substance that covers most of Earth and fills every cell, water keeps revealing electronic personalities when squeezed into flat atomic corridors. 

These findings remind us that even the most familiar liquid can behave in unexpected ways once we control matter on the tiniest scales.

The study is published in Nature.

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