University of Wisconsin–Milwaukee

Laura L. Hunt

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Dec 12, 2007 
RET links UWM resources with high schools

Lian Li and AFM
Tim Moeller (left), physics teacher at Hamilton High School in Sussex, and Physics Professor Lian Li recently demonstrated the Atomic Force Microscope (AFM) to Moeller’s students. Moeller learned to use the AFM as a participant in the Research Experience for Teachers (RET) program at UWM this summer.

Hamilton Student with ATM
Moeller shows Hamilton senior Alex Schwartz a model he constructed to illustrate how the AFM works. The pencil represents the tip. Moeller is adjusting the laser beam that reflects off the mirror near the tip to track the movement of the arm.

Photos by Laura L. Hunt
Most high school students know that a CD-ROM or a DVD holds much more information than a record album. But “how” is the question teacher Tim Moeller at Hamilton High School in Sussex put to his students.

To help with this assignment Moeller would not only explain it, he would show them.

He asked UWM physicist Lian Li and instrument specialist Donald Robertson to bring to his classroom a piece of equipment capable of providing a picture right down to the atomic level: an Atomic Force Microscope (AFM).

Moeller used this non-ocular apparatus during the summer when he participated in a program at UWM in which he became the student again.

Funded by the National Science Foundation (NSF), the Research Experience for Teachers (RET) program gives high school instructors the chance to conduct advanced research alongside a UWM faculty member. UWM’s program will operate for at least two more summers.

“The experience recharged me,” Moeller says, who described RET as a remedy for teacher burnout. “To be associated with brilliant people doing amazing things – [for me] it’s success by association. The challenge is to formulate a high school lesson from it.”

Working with Li, Moeller learned to operate and troubleshoot the AFM to image a piece of the information side of the discs. Once he mastered that, Moeller then came up with a way to teach his students about data storage in the digital age.

The AFM images atoms on surfaces to provide a super-magnified view of the normally unseen world. It works by scanning a fine tip – typically made of silicon using nanofabrication methods – over the surface of a sample. The tip is attached to the end of an arm that vibrates very quickly.

In response to the forces it encounters at the surface it is moving over, the arm’s motion is tracked by a laser that reflects at an oblique angle from the very end of the arm. This allows the laser to “draw” a profile of the surface of the sample.

How does it know when the topography changes? “It is the change in vibration frequency at each point that tells you the high and low spots,” says Li.

There are all kinds of forces at the atomic scale, says Li, citing electrostatic and magnetic as two.

Moeller used the demonstration as part of a series of lessons on methods of data storage, comparing analog to digital in the end. On a record album, the data is stored in the grooves. But on a CD-ROM, the data shows up as a spiral path that is either pitted or flat, allowing the data to be digitized.

The tiny pits are roughly the size of bacteria, he says.

So the assignment for Moeller’s students was to calculate the length of the spiral on a CD-ROM – which determines the amount of data that can be stored there.

“The answer will blow their minds since it comes out to be about 3.5 miles, compared to the 350 meters for the groove in a record album,” he says.

Four or five teachers are selected to participate in the RET each summer through 2009, and are paid a stipend, says UWM’s RET coordinator Robert Wood. Three other teachers participated last summer in research that was interdisciplinary between the departments of geosciences and physics.

In addition to Li, faculty mentors from physics included Prasenjit Guptasarma, Valerica Raicu, Carol Hirschmugl and Jean Creighton. From geosciences faculty included John Isbell, Barry Cameron, Tim Grundl, Margaret Fraiser, Steve Dornbos and Bill Kean.

Information on RET recruitment for 2008 will be available on the Department of Physics website in mid-January ( or by emailing