Researchers with the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, Germany, are investigating which liquid crystals are most suitable for use as lubricants, and under what conditions. The effort is a joint project with the Fraunhofer Institute for Applied Polymer Research IAP in Potsdam, and the Mainz-based company Nematel, both also in Germany.
Andreas Kailer, head of department at IWM, told Lube Report that liquid crystal lubricants have the potential to replace common slide bearing oils and similar lubricating oils in applications such as linear bearings, radial bearings and bearings for microsystems. We hope to be able to market a liquid crystal lubricant in three to five years time, he said. One typical use for slide bearings is in slide ways and guide ways of machine tools. They are also used in steel fabrications and buildings and in industrial plants.
Liquid crystals have not been suitable as a lubricant for ball bearings, he noted, as the contact pressure is too high so the friction does not drop far enough. For slide bearings though, liquid crystals may be a perfect solution, Kailer emphasized.
Slide bearings are a type of bearing that typically use low-friction materials such as Teflon and graphite for linear movement and weight bearing. Most slide bearings use a sandwich design of two plates of low-friction material mounted between metal backing plates.
The German research teams testing unit exerts a certain amount of force on a clamped metal cylinder that is moved back and forth over a supporting contact surface. He said the research program started about one and a half years ago.
The main advantage a liquid crystal lubricant can offer is an extremely low friction coefficient, Kailer noted. We need to do some more tests and qualifications to find out and eliminate drawbacks in using the crystals as a lubricant, he added.
Kailer said the other goals of the research include developing liquid crystal lubricants, in cooperation with lubricant manufacturers; analyzing and studying the fundamentals and theory of liquid crystal lubrication; and demonstrating its effect in different applications.
This lubricant is made from liquid crystals like the ones we know from flat-screen monitors, he explained. 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. Changing the molecule orientation makes it possible to change the optical and mechanical properties of the liquid crystals.
Liquid crystals produced for computer monitors must be ultra-pure, he said, which has made them very expensive to produce to this point. So one goal of the research is easy and cost-efficient synthesis of liquid crystals, in cooperation with suppliers, as less pure liquid crystals remain suitable as lubricants.