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Finding a new way to ease microscopic friction

By Kari VanDerVeen
August 26, 2008

When you're working on a machine that is smaller in size than a width of a hair -- such as the launch sensor in your car's airbag or accelerometer found in the controllers of games like Nintendo Wii -- using motor oil or WD-40 isn't an option.

Those everyday lubricants would prevent the machine from moving at all, explains St. Olaf Assistant Professor of Physics Brian Borovsky. For years scientists have relied on extremely thin lubricant films, consisting of slippery hydrocarbon layers just one molecule thick, to reduce friction and keep parts moving inside tiny machines known as microelectromechanical systems (MEMS), or micromachines. But these films haven't been sufficiently effective in machines with more advanced designs -- those that rely on moving parts in contact with each other, such as gears, hinges and pistons. That's why Borovsky has teamed up with researchers at Luther College and Auburn University to study a new type of lubricant film.

The films they are researching can be applied to metal oxide surfaces. Currently, micromachines are almost always made from silicon, a material that has proven notoriously unreliable for mechanical purposes. "Many people would like to see alternative materials developed for building micromachines as a way to improve performance and reliability," Borovsky notes. "These new materials, including the metal oxides we plan to investigate, will need lubricant films tailored to their needs."

The research proposal captured the attention of the National Science Foundation, which provided Borovsky with a grant of $116,444 for the project. He is working on this research with Luther College Assistant Professor of Physics Erin Flater and Auburn University Assistant Professor of Chemical Engineering W. Robert Ashurst. The total award for all three collaborating institutions is $200,000. The team plans to perform research during the summers of 2009 and 2010, and Borovsky notes that students will be heavily involved in the project.

"St. Olaf students will be involved in all aspects of this research, from taking data to performing analysis to presenting our results to wider audiences," he says, adding that some of the techniques and equipment used in this research will also be incorporated into advanced experimental physics courses on campus.

To perform the research, Borovsky and students at St. Olaf will use a special force probe called a nanoindenter in conjunction with a device known as a quartz microbalance. "Our integrated nanoindenter-quartz microbalance is a unique apparatus unlike what is found in other laboratories dedicated to studying friction," Borovsky says, noting that the quartz crystal oscillates five million times per second to achieve speeds comparable to the fastest micromachines. "Some more traditional techniques operate a million times slower than this."

Ashurst's group will prepare the research samples this spring and the groups working under Flater and Borovsky will use their state-of-the-art friction measurement systems to conduct experiments over the next two summers. Flater's group at Luther will use an atomic force microscope to test the same surfaces as Borovsky's group. The goal is to study the frictional properties of the various samples over the full range of speeds that might be encountered in actual micromachines.

"Our proposed studies seek to bridge the gap between the fundamental science of friction and the engineering of practical devices," Borovsky says. "This kind of effort has become all the more important as machines have shrunk to sizes so small that entirely new questions are raised about how to keep them moving and protected from wear or breakage. By combining two physicists and an engineer, along with our great crew of student researchers, we feel we have the right team assembled to address these questions."

Contact Kari VanDerVeen at 507-786-3970 or