Discovery of a law of friction leads to a material that minimizes energy loss

Researchers at the NYU Tandon School of Engineering have discovered a fundamental friction law that is leading to the design of two-dimensional materials capable of minimizing energy loss, according to a press release from the institution published on Thursday.

Friction lies behind the invention and development of many of today's most advanced technologies, however, its fundamental laws remain obscure to this day despite many developments in the field. In fact, it was only recently that scientists were able to use advances in nanotechnology to understand the physics behind the microscopic origin of da Vinci's law, which holds that frictional forces are proportional to the applied load.

Now, professor of Chemical and Biomolecular Engineering Elisa Riedo and postdoctoral researcher Martin Rejhon have stumbled upon a new way to measure the interfacial shear between two atomic layers. They also further found evidence of a new law that indicates that this quantity is inversely related to friction.

A new law discovered

"The interaction between a single atomic layer of a material and its substrate governs its electronic, mechanical, and chemical properties," Riedo explained in the statement.

"So gaining insight into that topic is important, on both fundamental and technological levels, in finding ways to reduce the energy loss caused by friction."

To discover the new law, the scientists looked at bulk graphite and epitaxial graphene films and measured the hard-to-access interfacial transverse shear modulus of an atomic layer on a substrate.

The modulus refers to a measure of the material's ability to resist shear deformations and remain rigid, and the researchers' results showed that it is largely controlled by the stacking order and the atomic layer-substrate interaction.

This modulus is also crucial in controlling and predicting sliding friction in supported two-dimensional materials. The researchers uncovered a general reciprocal relationship between friction force per unit contact area and interfacial shear modulus.

Promising results

"Our results can be generalized to other 2D materials as well," Riedo, who also heads NYU Tandon's PicoForce Lab, explained.

"This presents a way to control atomic sliding friction and other interfacial phenomena, and has potential applications in miniaturized moving devices, the transportation industry, and other realms."

The new discovery can be used to control the unwanted effects of friction that drive the waste of large amounts of energy in industrial processes, the transportation sector, and elsewhere.

It has been estimated that one-quarter of global energy losses are due to friction and wear. This is a major energy loss that, if overcome, might result in a more efficient and environmentally friendly field.

"Elisa's work is a great example of NYU Tandon's commitment to a more sustainable future," said Jelena Kovačević, Dean of the NYU Tandon School of Engineering.

She added that the work was "a testament to the research being done at our newly launched Sustainable Engineering Initiative, which focuses on tackling climate change and environmental contamination through a four-pronged approach we're calling AMRAd, for Avoidance, Mitigation, Remediation, and Adaptation."