Chinese Scientists Observe Quantum Friction Between Solid Surfaces in Folded Graphene

Folded Graphene Reveals an Unexpected Source of Friction

Chinese scientists at the Lanzhou Institute of Chemical Physics have directly observed quantum friction between two solid surfaces for the first time, using folded graphene to examine how motion loses energy at the atomic scale. Their experiment found an unexpected pattern: adding more layers did not always increase friction, and some thicker folds slid more easily than thinner ones.

The findings, published in Nature Communications, connect that behavior to changes in the electronic structure of graphene. Folding the material creates strain that reorganizes the energies available to electrons. Those changes can reduce the transfer of energy into vibrations, lowering the amount of motion lost as heat.

The research team described the achievement in a statement on social media:

This is the first experimental evidence of quantum friction between two solid surfaces.

As of July 28, 2025, the work offers a way to study how quantum effects influence friction in a solid interface. It also opens possibilities for machines that consume less energy and for a new generation of devices with moving parts measured at the nanoscale.

What Makes This Friction Different?

Friction resists motion when surfaces slide against each other. It gives car tires their grip on a road and contributes to the creaking of knees. The familiar explanation focuses on microscopic bumps and sticky patches: as surfaces move, these interactions turn some of their mechanical energy into heat.

For centuries, surface roughness provided the main explanation for that resistance. At the nanoscale, however, the behavior of atoms and electrons introduces processes that this classical picture cannot fully describe.

Quantum friction arises from quantum mechanical interactions involving atoms, electrons and even the vacuum itself. It can occur between perfectly smooth surfaces or across tiny gaps, through fluctuations in electromagnetic fields or changes in the quantum states of electrons. Surface roughness and direct contact dominate ordinary friction, while these additional processes become relevant at much smaller scales.

Scientists had largely studied quantum friction as a theoretical concept. They had predicted its role in liquids flowing over solids, including water moving through carbon nanotubes. Direct experimental evidence between two solid surfaces had been lacking. The folded graphene experiment brings that investigation into a solid interface whose shape and electronic behavior can be controlled.

Why the Team Chose Graphene

Graphene consists of a single layer of carbon atoms arranged in a honeycomb lattice. Since its isolation in 2004, it has attracted scientific interest because it is extremely strong, flexible and a better conductor of electricity than copper.

The Lanzhou researchers used that flexibility to fold very thin graphene sheets, producing edges with controlled curvature and different numbers of layers. They then examined how friction changed under those conditions with atomic force microscopy and spectroscopy.

Atomic force microscopy measures interactions at extremely small scales, allowing researchers to probe the folded edges. Spectroscopy helps investigate the material's electronic behavior. Together, these methods let the team connect a measured change in friction with changes taking place inside the graphene.

Folding also changes how electrons move through the material. A flat sheet and a curved, strained fold can have different electronic states. That makes the fold more than a mechanical bend: it becomes a means of adjusting the quantum behavior that influences energy loss.

• 2004: Graphene was isolated, opening the way to studies of its strength, flexibility and electrical conductivity.
• By July 28, 2025: The Lanzhou team's findings on quantum friction in folded graphene had been published in Nature Communications.

Thicker Folds Did Not Always Mean More Resistance

The researchers measured friction at the edges of folded graphene using atomic force microscopy. They expected friction to increase linearly with the number of layers under the classical description used for the experiment. A linear increase would mean that adding layers produced a proportionate rise in resistance.

The measurements followed a different pattern. In some cases, folds containing more layers slid more easily than thinner folds. This nonlinear behavior directed attention toward changes in the electronic structure rather than the number of layers alone.

Spectroscopic investigations showed that the strain created by folding generated strong pseudo-magnetic fields inside the graphene. These produced pseudo-Landau levels, discrete energy states associated with the altered movement of electrons.

The resulting quantum states suppressed the usual routes through which motion loses energy. In particular, they reduced the coupling between electrons and vibrations in the material, known as phonons. With less energy passed into those vibrations, less was converted into heat and friction fell.

How a Bend Changes the Energy Available to Electrons

Pseudo-Landau levels are separate energy states that electrons occupy because of strain in the graphene. The term describes an effect that resembles the action of a magnetic field, even though the mechanism here comes from deforming the material.

The curvature and strain of a fold force electrons into these discrete levels. Rather than allowing energy to pass along the usual routes into the material's vibrations, the altered electronic states restrict that transfer. The original explanation likens the levels to quantum speed bumps: they make it harder for electrons to dissipate energy as heat while the material moves.

Phonons are vibrations within a solid. Coupling between electrons and phonons means that energy can pass between the electronic system and those vibrations. Reducing that coupling limits one route for energy loss, helping explain why friction can fall at a folded edge.

The effect also changes with the number of layers. As more folded layers are added, the pseudo-magnetic field weakens and the influence of the pseudo-Landau levels diminishes. Eventually, friction returns to a more classical, linear pattern.

This transition gives researchers a way to examine how quantum behavior can be adjusted in a real material. Changing the fold and its layers changes the strength of the electronic effect, which in turn changes the resistance to motion.

Water and Carbon Show a Related Quantum Connection

The graphene experiment builds on research into quantum friction where a solid meets a liquid. In those systems, water can interact directly with electrons in graphene, affecting how quickly it flows over a graphene surface or through a carbon nanotube.

Vibrations of water molecules, called hydrons in this explanation, can match the collective oscillations of electrons in graphene, called plasmons. When those motions resonate, energy transfers more readily between the water and the carbon material, increasing friction.

The process depends on the combination of materials. The same resonance effect is not observed with ethanol or methanol. Water's interaction with the electronic behavior of carbon therefore provides a specific mechanism for changing resistance at the boundary between a liquid and a solid.

Researchers at the Max Planck Institute for Polymer Research described that relationship:

Water and carbon form a quantum couple where the flow of water on a carbon surface is influenced by quantum friction, an unusual phenomenon.

An expert from the University of Manchester, commenting on the experiments involving water, described their scientific importance:

It is impressive that quantum phenomena usually occurring in solids appear in what would be considered a classical liquid as water. The experiments thus confirm the basic mechanism of solid-liquid quantum friction.

The folded graphene work extends the investigation to an interface between solids. Together, these studies show how electronic behavior can influence friction in different kinds of contact, with quantum processes either increasing energy transfer or suppressing it.

Why Water Can Flow Faster Through Narrower Nanotubes

Carbon nanotubes are tiny pipes made from rolled sheets of graphene. Experiments have shown that water flows much faster through narrower nanotubes, a result that runs against classical expectations.

Quantum friction theory provides an explanation: fewer electrons are available to interact with water in narrower tubes. That reduces resistance and allows the water to flow faster.

The finding connects a puzzling flow pattern to interactions between water and the carbon wall. It also gives researchers a possible route to designing membranes that control the movement of water by controlling energy transfer at their surfaces.

Nanofluidics, the study of fluid flow at the nanoscale, is one field that could benefit. More precise control of friction could help the development of filtration and desalination technologies, as well as membranes for water purification and energy generation.

What Controlling Friction Could Change for Devices

Machines with tiny moving parts can lose useful energy through friction and suffer wear at their points of contact. Reducing that resistance could lower power consumption and extend the life of nanoscale machines.

Traditional lubricants are ineffective in this setting, where even small energy losses can matter. Controlling the electronic processes responsible for part of the friction offers another approach to managing those losses.

Related research has demonstrated that carboxylated graphene quantum dots can produce superlubricity, a state of extremely low friction, in steel contacts. Those experiments reduced wear by up to 69 percent, pointing toward lubrication technologies that use less energy and are more environmentally friendly.

The folded graphene findings suggest possible uses in switches, valves, pumps and sensors that operate with minimal energy loss. Controlling quantum friction could also help devices that convert mechanical motion directly into electrical energy.

Electronics and quantum computing provide further reasons to investigate energy dissipation. Devices that consume less power need careful management of energy loss, while quantum bits, or qubits, and related technologies depend on maintaining stability and efficiency. The broader goal is to design devices approaching operation without dissipating energy.

What Researchers Still Need to Resolve

Quantum friction is a subtle effect that often requires very low temperatures and precise experimental arrangements to observe. Bringing useful control of these effects to room temperature and more complex environments remains a major research challenge.

The next stages of investigation include testing whether similar behavior occurs in other materials and under different conditions. No dates were given for those steps. Researchers also seek a framework that can predict and control quantum friction across a wider range of systems.

Other studies examine interactions between neutral particles and surfaces in a quantum vacuum. Some approaches look for small corrections to the geometric phase, a property that quantum systems accumulate over time. Those measurements offer another route to investigating subtle friction effects.

Folded graphene provides a more tangible and controllable experimental system. Its shape and layer count can be adjusted, allowing researchers to study how the electronic states and measured resistance change together.

The discovery has been greeted with enthusiasm because it connects fundamental physics with a practical materials problem. The Chinese team's experiment shows that quantum friction at an interface between solids can be measured and manipulated, bringing the possibility of controlling energy loss closer to experimental investigation.

Key Points

• Researchers at the Lanzhou Institute of Chemical Physics directly observed quantum friction between two solid surfaces using folded graphene.
• Some thicker folds slid more easily than thinner ones, departing from the expected linear increase in friction.
• Strain created pseudo-magnetic fields and pseudo-Landau levels that reduced energy transfer between electrons and material vibrations.
• Adding more layers weakened the quantum effect, eventually returning friction to a more classical pattern.
• Related water and carbon studies connect quantum friction to nanotube flow, filtration and desalination.
• Potential applications include nanoscale machines, lubrication, electronics and quantum computing, with further work needed on materials and operating conditions.