The natural mechanical properties of natural joints are considered unrivalled. Cartilage is coated with a special layer of lubrication that allows joints to move virtually friction-free, even under high pressure. Using simulations on supercomputers, scientists from Forschungszentrum Jülich in Germany and the University of Twente, Enschede,Netherlands, have developed a new process that technologically imitates biological lubrication and even improves it using two different types of polymers.

Lubricants are required where moving parts come together. They ensure that gears, bearings, and valves work as smoothly as possible. Depending on the application, the ideal lubricant should be as thin as possible to reduce friction, but also must be viscous enough that its stays in the contact gap.

Grease and oils are usually used because their viscosity increases with pressure. However, biological lubrication is much more efficient. In joints, a thin, watery solution prevents friction. The thin film stays where it should because a polymer layer is anchored to the cartilage and forms "polymer brushes," which attract the extremely fluid lubricant and keep it in place at the contact point.

Over the last 20 years, numerous attempts have been made to imitate the natural model technically. But the tentacle-like polymers on surfaces opposite each other get tangled, detach from the surfaces, and do not possess self-healing mechanisms.

The researchers decided to try using two different polymers at the contact point to prevent the polymers from becoming entangled. Using supercomputers, they simulated applying water-soluble polymers to one side and water-repellent polymers to the other side. This combination reduced the friction by two orders of magnitude, compared to using just one type of polymer, they said.

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