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A means for tuning friction on a flat surface without the use of math

A means for tuning friction on a flat surface without the use of math
The image shows an artist view of a metainterface between a rigid smooth transparent solid on the top and a soft rough solid on the bottom. Textured ellipses represent real contact regions. The topography is made of an array of spherical asperities, each with a specifically designed height. Credit: Nazario Morgado

A team of microsystems engineers at Université de Lyon, École Centrale de Lyon has developed a method to create a desired amount of friction between two flat surfaces without resorting to math. Their project is reported in the journal Science. Viacheslav Slesarenko and Lars Pastewka, both with the University of Freiburg, have published a Perspective piece in the same journal issue, outlining the work done by the team in France.

Friction, the drag produced when two materials are pressed and moved against one another, has become a major factor in the design of modern electronic properties. From the of a finger swipe across a phone screen to sensors under development for robot hands, friction and its measurement and control have become a big concern for .

Unfortunately, despite its ubiquity, calculating friction coefficients is still a challenging proposition due to the vast number of characteristics of individual materials. In this new effort, researchers in France have found a faster way to obtain the desired amount of friction between two flat objects.

The movie shows a qualitative illustrative experiment showing that two metainterfaces may have either similar or different frictional behaviors, depending on the range of normal force applied. The low normal force corresponds to the weight of the bare samples, about 5 g. The large normal force corresponds to an additional weight of about 10 g (rectangular polymer plate placed on top of each sample). For each normal force, both samples are driven by the same tangential displacement, ∆, through loading springs. When the samples are sliding (non-vanishing sliding distances SR and SB), the spring lengths (LR and LB) enable visualization of whether the friction forces are similar or different. Credit: Davy Dalmas & Julien Scheibert

Most of the friction involved between two is due to projections on one or the other surface. When tiny bumps on one surface collide with the tiny bumps on another, they must overcome one another to allow for sliding. The innovative work by the team involved creating a type of with adjustable bumps.

To create their surface, the research team used a rubber-like elastomer, which they describe as a metainterface due to its adjustable bumps, each of which can be individually adjusted by height. By altering the heights of the bumps, the team was able to alter the amount of friction produced when another flat was pressed against it and then slid to one side. The researchers found that by adjusting the height of the bumps in a systematic way, they could zero in on the amount of friction desired.

A means for tuning friction on a flat surface without the use of math
The image shows a sketch of a metainterface between a rigid smooth transparent solid on the top and a soft blue rough solid on the bottom. Dark gray ellipses represent real contact regions. The topography is made of an array of spherical asperities, each with a specifically designed height. The red arrow shows the direction of motion applied to the top solid to probe the friction behavior of the metainterface. Credit: Nazario Morgado

They tested their metainterface by placing a glass pane on top of it, applying pressure, and then sliding it to one side and then the other. Using this approach, they found that they could not only create materials with the desired degree of friction, but also demonstrate several friction laws.

More information: Antoine Aymard et al, Designing metainterfaces with specified friction laws, Science (2024). DOI: 10.1126/science.adk4234

Viacheslav Slesarenko et al, The bumpy road to friction control, Science (2024). DOI: 10.1126/science.adn1075

Journal information: Science

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Citation: A means for tuning friction on a flat surface without the use of math (2024, January 19) retrieved 28 April 2024 from https://phys.org/news/2024-01-tuning-friction-flat-surface-math.html
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