How did you become interested in nanotechnology? Did you have an epiphany or did your interest gradually grow?
"My interest in nanotechnology gradually grew out of a need to understand why physics seems so different at small and large scales and how the two connect with each other. This interest evolved into a desire to make discoveries of my own while taking part in a field that has direct positive social and political impact."
What do you plan to do when you finish your degree?
"At the moment, I am still searching for the path that is right for me, though there are many possible routes that are appealing, including careers in academia, industry and public policy. I strongly believe in the importance of education and outreach objectives that bridge the gap between disciplines and social groups and that improve the average quality of life. I hope that these things will play major roles in my career as a scientist."
What advice would you give to someone (a college or high school student) who is interested in pursuing nanotechnology research?
"I would encourage them to develop their thoughtfulness, creativity, and ability to communicate with diverse audiences. Analytical skills are important, but being able to answer why something should be pursued, to address its downfalls, and to consider multiple paths are invaluable traits useful in everything we do. I used to want to pursue a career in art, but then I switched to physics, and in doing so I have found creativity to be just as important in science as it is in art. I would also encourage students to take a lot of math. It's a really important tool if you want to be in any science. In college, find a lab that hires undergraduates and work for a professor or graduate student. I learned the most by experiencing first-hand the ups and downs of a research project. And I'm still learning!"
- http://www.fearofphysics.com/Friction/frintro.html
- - an introduction to friction
- http://www.nano-world.org/frictionmodule/content
- - an in-depth look at friction
- http://silver.neep.wisc.edu/~cannara
- - Rachel's web-site
Rachel Cannara: Diamonds in the Basement
Greta M. Zenner
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Rachel examining research images on her computer |
Rachel Cannara works in the basement, a situation she likes. "There are fewer vibrations down here," says the flame-haired fourth-year physics graduate student at the University of Wisconsin-Madison (UW). Most people wouldn't find such subtle differences in vibration an important issue in their daily lives. Rachel, however, who works in the Engineering Physics Department at the UW for Professor Robert Carpick, prefers the conditions because she studies vibrations and their effect on friction at a very small scale - the scale of the atom. Conducting her research in the basement gives Rachel more control over her experiments. |
Rachel and other scientists believe that by studying friction at the atomic scale, or the nanoscale, they can find its fundamental causes, which will help other nanotechnologists create new materials and improve already existing ones. "Knowing more about friction gives us more control. We're hoping that we can someday tailor surfaces to have a desired friction, or no friction, which would ultimately help us save energy," says the UW graduate student.
Friction occurs when two surfaces slide past each other. Although the phenomenon is familiar to us all - try rubbing your hands on your jeans and notice the resistance and resulting warmth - scientists don't fully understand what causes friction or how it works.
Scientists do know that friction at the nanoscale is different than at the macroscale, the scale of the jeans experiment. At the macroscale, tiny bumps invisible to the naked eye drag across each other, interact, and create friction. The question remains, however, what exactly is happening when the bumps interact? To answer this, researchers like Rachel turn to the nanoscale, where surface area and contact area become extremely important. As the ratio of surface area to volume grows going from the macro to the nanoscale, the interaction of surface forces become more significant than other forces like gravity or inertia, which play major roles on the macroscale. |
A cartoon close-up of micro-scale bumps rubbing against each other and causing friction |
Consequently, Rachel studies extremely smooth surfaces in order to find out how the surface interactions of two materials create and affect friction. If she were to use bumpy materials, her research would still address issues important to the macroscale, like gravity and inertia. Smooth surfaces allow her to get to the basics of friction.
For Rachel, the fundamentals are the most interesting part about her research. "I want to understand the big picture behind friction - what the physical laws are that govern a material sliding on another material. I have a physics background. I like to know how things work."
Currently, scientists researching nanoscale friction believe it has two possible dominant causes - vibrations, such as heat and sound, and electronic interactions, a phenomenon where electrons create a resistance to sliding. To narrow her research project, Rachel investigates sound vibrations, or phonons, in solids. She gathers experimental data that she hopes will support the hypothesis that phonons influence friction. To do this, Rachel studies crystals that contain varying concentrations of the different stable isotopes of carbon. Isotopes are atoms that are the same except for their masses. Two isotopes of the same element have the same number of protons and electrons, but different numbers of neutrons. In Rachel's research, she looks at crystals of carbon atoms (in her case, diamonds) that are exactly the same, except that each of the crystals is made up of different ratios of carbon isotopes. |
Sample holders for the AFM |
Inside the AFM |
Rachel examines the diamonds with an atomic force microscope, or AFM. The AFM is a very sensitive microscope that allows scientists to see surfaces at the atomic level. When Rachel looks at her samples, the AFM drags an extremely fine probe across the diamond surface. By observing how the nanometer-sized tip causes its lever to twist and bend as it interacts with the atoms on the surface of the sample, Rachel can obtain a precise measurement of friction at the atomic scale. |
An AFM tip and cantilever Image courtesy of MikroMasch, |
An AFM image of the diamond surface |
She then compares the AFM data with information already known about the material's sound vibrations. Rachel does this for several different samples and looks for any trends between the AFM data and the phonon properties of the surface. Eventually, Rachel's work will either support or refute her hypothesis that vibrations affect friction.
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Rachel adjusts the AFM |
An AFM image of diamond |
In addition to satisfying her scientific curiosity, Rachel's research also has other applications. In particular, notes Rachel, miniature machines of the future could benefit. As currently designed, these devices, called micro-electro-mechanical systems, or MEMS, can only be used for short periods of operation, if that, before their tiny gears stick together and cause the machine to break down. The research Rachel and other scientists conduct has the potential to decrease friction at the atomic scale, which would increase the lifetime of MEMS devices and, in the future, even nano-electro-mechanical devices (NEMS). Improving these tiny machines is an important goal of nanotechnology given their promise of numerous applications in medicine, communications, defense, and consumer products. For Rachel, it is possibilities such as these, along with the excitement of conducting her own research, that make the basement a worthwhile place to be. |
An interview with Rachel
Additional Information
David Adams, "Nano-Lubrication: Facts and Friction," a news @ nature article, December 7, 2000
Copyright © 2004 The Board of Regents of the University of Wisconsin System.
This page created by Greta Zenner. Last modified May 4, 2005.