‘Boundary lubrication is common in machines but is also thought to act between joints and other living organs in the form of phospholipid films,’ said Professor Jacob Klein. ‘This new mechanism could lead to better lubricated artificial implants, as well as to more effective treatments for joint problems like osteoarthritis.’
Professor Klein and his colleagues at the Physical and Theoretical Chemistry Laboratory at Oxford reported their discoveries in the 9 November issue of the journal Nature.
For more than fifty years, films or layers which are one molecule thick have been used in air or oil to lubricate surfaces which rub together, reducing friction and wear. These layers have usually belonged to the class of amphiphilic surfactants, whose head is water-loving, while their tail is water-repelling.
‘Each of the rubbing surfaces is coated by a “boundary” layer of surfactant molecules, with charged heads that stick to the surface while their hydrocarbon tails dangle out,’ explained Professor Klein. ‘In classical boundary lubrication in air or oil, the rubbing occurs between these protective tails and greatly reduces friction and wear.’
The Oxford researchers studied the friction between mica surfaces in the different environments, with and without overlaying surfactants. They have shown that the friction stress between two sliding surface coated by surfactant monolayers can decrease much more in water than in air or oil, falling to one percent or less of its value for the latter environments.
‘We believe this happens because the charged head groups then become hydrated, that is, coated with water molecules,’ said Professor Klein. ‘This enables them to slide much more easily past the substrate than the hydrocarbon tails can slide past each other. As a result, the slip occurs at the substrate, rather than between the surfactant tails as in the classical mechanism.’
The researchers proved that the hydration of the anchors must be largely responsible for the reduction in friction by testing surfactants which were homologous to the original but could not be fully hydrated at the surface because of their structures, which resulted in greater friction. They also eliminated the possibility of this occurring due to the flipping of the surfactants’ anchors when they came into contact with water by performing the same experiments on surfaces which were brought into adhesive contact before being immersed, so that the anchors could not flip.
Barbara Hott | alfa
Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH
Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences