How is this new Vitreous coating lubricant different from other methods used to lubricate bearings and gear trains? “This lubricant is made from liquid crystals like the ones we know from flat-screen monitors,” said Dr. Andreas Kailer, head of department at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg. “In contrast to normal liquids, the molecules in liquid crystals have a certain orientation – you might compare them to matches with their heads all pointing in the same direction.”

In a joint project with the Fraunhofer Institute for Applied Polymer Research IAP in Potsdam and the Mainz-based company Nematel, the IWM researchers are investigating which liquid crystals are most suitable for use as lubricants, and under what conditions. To test and verify the performance of liquid crystal lubricants a test coupon is applied with a known and controlled amount of force onto a clamped metal cylinder that is reciprocated over a contact surface. The friction and subsequent wear of the test coupon is documented and most importantly which lubricant does the machine require the smallest amount of energy to move the metal cylinder?

Typically dynamic friction changes minimally with conventional oil, however an almost zero friction measurement can be obtained when liquid crystals are used. The time frame that this takes depends primarily on the pressure with which the reciprocating cylinder is pressed against the coupon contact surface. If you were to compare the testing coupon application it to a child on a playground slide, it would correspond to the weight of the child sitting and sliding down the playground slide. “Liquid crystals have not been suitable as a lubricant for ball bearings until now, as the contact pressure is too high – the friction does not drop far enough. “For slide bearings, on the other hand, liquid crystals are the perfect solution,” says Kailer. Since liquid crystals have been produced mainly for monitors up to now, they have to be ultra-pure – which makes them very expensive. So the researchers now plan to simplify the synthesis process, since less pure substances are also suitable as lubricants,. “We hope to be able to market a liquid crystal lubricant in three to five years’ time,” says Kailer.

Image: Testing machine utilized by the researchers to examine liquid crystals as lubricants: (Credit: Copyright Fraunhofer IWM, Fraunhofer-Gesellschaft)