Lubricants are required wherever moving parts come together.
They prevent direct contact between solid elements and ensure that gears, bearings, and valves work as smoothly as possible. Depending on the application, the ideal lubricant must meet conflicting requirements. On the one hand, it should be as thin as possible because this reduces friction.
On the other hand, it should be viscous enough that the lubricant stays in the contact gap. In practice, grease and oils are often used because their viscosity increases with pressure.
Biological lubrication in contrast is much more efficient. In joints, a thin, watery solution prevents friction. The thin film stays where it should thanks to a trick of nature. A polymer layer is anchored to the cartilage at the end of bones. Polymers are a string of densely packed, long-chain molecules.
They protrude from the cartilage and form "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 with no resounding success. The tentacle-like polymers on surfaces opposite each other tend to get tangled up in each other.
They slow each other down and detach from the surfaces. In technical systems, individual polymers that become detached are difficult to replace as they do not possess the same self-healing mechanisms as in a natural organism.
Jülich physicist Prof. Martin Müser came up with the idea of using two different polymers at the contact point to prevent the polymers becoming entangled. "Using supercomputers, we simulated what would happen if we applied water-soluble polymers to one side and water-repellent polymers to the other side," says head of the NIC (John von Neumann Institute for Computing) group Computational Materials Physics at the Jülich Supercomputing Centre (JSC)."
This combination of water-based and oil-based liquids as a lubricant reduced the friction by two orders of magnitude – around a factor of 90 – compared to a system comprising just one type of polymer."
Measurements with an atomic force microscope at the University of Twente in the Netherlands verified the results. "The two different phases of the liquid separate because they repel each other. This simultaneously holds the polymers back and prevents them from protruding beyond the borders," says Dr. Sissi de Beer, who recently moved from Müser's group to the University of Twente.
The low-friction two-component lubricant is interesting for numerous applications. One example are simple piston systems, like syringes, which are used to precisely administer even tiny amounts of a drug.
Above all, the new process could provide low-friction solutions where high pressures and forces occur locally – for example, axle bearings and hinges. For the most common lubricant – engine oil – an alternative has yet to be found; conventional polymer brushes are unable to withstand the high temperatures.
Tobias Schlößer | Eurek Alert!
Single atom alloy platinum-copper catalysts cut costs, boost green technology
09.10.2015 | Tufts University
Controllable protein gates deliver on-demand permeability in artificial nanovesicles
09.10.2015 | Universität Basel
Nondestructive material testing (NDT) is a fast and effective way to analyze the quality of a product during the manufacturing process. Because defective materials can lead to malfunctioning finished products, NDT is an essential quality assurance measure, especially in the manufacture of safety-critical components such as automotive B-pillars. NDT examines the quality without damaging the component or modifying the surface of the material. At this year's Blechexpo trade fair in Stuttgart, Fraunhofer IZFP will have an exhibit that demonstrates the nondestructive testing of high-strength automotive body parts using 3MA. The measurement results are available in a matter of seconds.
To minimize vehicle weight and fuel consumption while providing the highest level of crash safety, automotive bodies are reinforced with elements made from...
The MICADO camera, a first light instrument for the European Extremely Large Telescope (E-ELT), has entered a new phase in the project: by agreeing to a Memorandum of Understanding, the partners in Germany, France, the Netherlands, Austria, and Italy, have all confirmed their participation. Following this milestone, the project's transition into its preliminary design phase was approved at a kick-off meeting held in Vienna. Two weeks earlier, on September 18, the consortium and the European Southern Observatory (ESO), which is building the telescope, have signed the corresponding collaboration agreement.
As the first dedicated camera for the E-ELT, MICADO will equip the giant telescope with a capability for diffraction-limited imaging at near-infrared...
Self-driving cars will be on our streets in the foreseeable future. In Graz, research is currently dedicated to an innovative driver assistance system that takes over control if there is a danger of collision. It was nature that inspired Dr Manfred Hartbauer from the Institute of Zoology at the University of Graz: in dangerous traffic situations, migratory locusts react around ten times faster than humans. Working together with an interdisciplinary team, Hartbauer is investigating an affordable collision detector that is equipped with artificial locust eyes and can recognise potential crashes in time, during both day and night.
Inspired by insects
An interdisciplinary team of researchers has built the first prototype of a miniature particle accelerator that uses terahertz radiation instead of radio...
At present, tiny magnetic whirls – so called skyrmions – are discussed as promising candidates for bits in future robust and compact data storage devices. At...
01.10.2015 | Event News
30.09.2015 | Event News
17.09.2015 | Event News
09.10.2015 | Earth Sciences
09.10.2015 | Life Sciences
09.10.2015 | Life Sciences