The world uses tens of millions of tons of lubricant every year, from the smallest part of a micro-precision instrument to the expansion rollers on the largest bridges. Most are oil based, though others use powders, and even metals, and it’s been that way for decades. That could be changing as the Fraunhofer Institute for Mechanics of Materials (IWM), Nematel GmbH, and Dr. Tillwich GmbH have developed a new class of lubricants that are based on liquid crystals instead of oil. According to Fraunhofer, this is the first fundamentally new lubricant developed in twenty years.
Liquid crystals are an oddity of the chemical world that most people know from digital displays and television sets, but are actually found in everything from cell membranes to soapy water. As the name implies, a liquid crystal is a substance that is neither entirely a liquid, nor a crystal, but possesses the properties of both, such as a liquid that retains the structure of a solid crystal.
It’s this structure that provides the new lubricant with its slippery quality. In a normal liquid, the molecules lay about in a random fashion, but a liquid crystal can line up its molecules in parallel, so when two surfaces are coated with a liquid crystal lubricant, they slide past one another as if on a set of microscopic rails that are nearly frictionless.
According to Fraunhofer, the new lubricants demonstrated very low friction surprisingly early in the tests, with the lubricant layers showing a high level of stability and very low wear thanks to the long, thin nature of the molecules. Testing was done using lasers designed to measure extremely low friction coefficients without having to make contact.
Fraunhofer hasn't released much about the specifics of the new liquid crystal lubricants, but the company says that the research team has been working with additives to increase the lubricant’s stability, as well as studying the chemical mechanism involved in ultra-low frictional coefficients and the adding together of different liquid crystal molecules. They've also been testing the lubricant in sliding bearings made of iron, copper, and ceramic.
Despite progress, Fraunhofer says that there’s still a long way to go before the new lubricant is suitable for practical applications. It isn't enough for a lubricant to just be slippery. It also needs to work in both high and low temperatures, have a reasonably high viscosity index, be thermally and hydraulically stable, and resist oxidation amongst other things.
When the project wound up, the team had created a liquid crystalline lubricant prototype that performed best in sliding bearings made of iron.The team is currently working on developing sliding bearings using the liquid crystal lubricant for small electric motors for the car industry.