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Faculty Profile: Rob Carpick — Measuring friction on a smaller scale

Professor Robert Carpick rubs his research the right way. The department's newest faculty member has studied the frictional and mechanical properties of thin polymer films (one to three molecular layers thick). "What is interesting about these films is that you can see how the molecular structure affects the friction force," he says. He compares the concept to train tracks. When you slide along the polymer linkage, like a train rolling down the tracks, friction is low, but friction becomes much higher, like crossing the tracks, when you slide across the polymer linkage. "The importance of this result is that it means you could potentially design surfaces where you could control the direction of sliding of materials on top of that surface," Carpick explains. "This could be useful for assembling very small, nanoscale components."
Robert W. Carpick

Robert W. Carpick (22K JPG)

He began this work as a postdoctoral researcher at Sandia National Laboratories in Albuquerque, New Mexico. Carpick's background is in physics (he holds a BSc from the University of Toronto and a PhD from UC-Berkeley), but he unknowingly began his transition to mechanics from the start. While at Berkeley, he worked under Miquel Salmeron, who'd received a grant to be one of the pioneers of nanotribology, the study of friction, adhesion and anything that involves contacting or sliding materials at the atomic scale.

Carpick's experiments involved measuring friction forces in a contact that was only a few nanometers wide. He discovered that the friction force in a nanoscale contact was proportional to the number of atoms in contact. "The exciting result was that certain classical theories of contact, developed for macroscopic-sized contacts, still work at the nanometer scale," he says. K.L. Johnson, renowned mechanics researcher, developed many of those theories, which Carpick referenced to analyze his own data.

Johnson, in turn, took an interest in Carpick's work. "He worked out an updated version of his theory, included our results in his paper, and has mentioned them in presentations," says Carpick. "Having someone of his stature take my work that seriously is an incredible honor."

Another facet of Carpick's research--his current work--is setting up an advanced scanning-probe microscropy lab and building his own customized scanning-probe instruments. The tools are like a miniature record player: Carpick puts a tiny tip (like a record needle) in contact with a surface, and measures the resulting friction, load, adhesion and other forces. "I plan to use this to study the nanoscale frictional and mechanical properties of organic thin films, micromachine surfaces and nanocomposite materials," he says.

Recently several engineering physics colleagues introduced the Winnipeg native to a less academic study in friction: the sport of curling. "Curling is familiar to anyone growing up in Canada and it was fun to finally get to try it out," he says. When he's not "sweeping the sheets," he's tickling the ivories. "I am an avid devotee of Baroque music--especially Bach and the composers in and around his generation," says Carpick. "Over the years, I have been learning to play the keyboard instruments of the period, namely the harpsichord, clavichord and the pipe organ. Playing music is incredibly relaxing and stimulating to me."

Carpick joined the department in January as part of an interdisciplinary cluster hire in nanoscale materials, measurements and devices. He felt that there was a good fit between his research and that of his EP colleagues. "I liked what I saw in EP, which was a vibrant and harmonious department with many people to interact with," he says.


EPISODE is published twice a year for alumni and friends of the UW-Madison Department of Engineering Physics.

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Date last modified: Friday, 16-Jun-2000 14:00:00 CDT