Dustin Carr

Investigating the Very Small

February / March 2005 By: Margaret Lovell Volume 3 Number 1

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Dustin Carr claims that while he was a creative kid, he was not really inventive or good at building things. He was much better, he says, at breaking things. In a way, Carr is continuing on the path as a researcher at Sandia National Laboratories, only now the things he's breaking are the boundaries of size and function as he contributes to Sandia's efforts in nanoelectromechanical systems (NEMS) and optics.
A new class of very small handheld devices uses light-wave interference to detect motion a thousand times more subtly than any tool known. "There was nothing in the literature to predict that this would happen," says Carr. Similar in operation to the shadow pictures projected onto a wall by shining light through the fingers of one hand moving over the fingers of the other, the relatively simple measuring device depends upon a formerly unrecognized property of optics: light diffracted from very small gratings that move very small lateral distances undergoes a relatively big, and thus easily measurable, change in reflection. A motion of 10 nanometers can be seen by the naked eye. "The device couldn't exist unless you made it this small," he says. Applications for a NEMS accelerometer could include devices to anticipate earthquakes or sense a skid where the back end of a car is moving in a different direction than the front end.
Dustin Carr's role as a leading scientist in a cutting-edge field was far from a sure thing. He says, "I changed my major to physics in my first summer session at college. I originally went to school to study management. I dropped out of high school before my senior year and stayed out of school for a couple of years before deciding to go on to college. I never thought that I would be a scientist until I started college and actually began to understand what physics was about."
That he understood physics very well was obvious when, as a graduate student, he invented the nanoguitar. According to Carr, "The nanoguitar is a demonstration of the technology that I developed while at Cornell. In my research I was studying vibrations in nanomechanical systems, and the guitar was a natural demonstration of this. I made it purely for fun; it was easy to make the pattern in parallel with other research devices that I was making on the same silicon chip. I never really intended to show it anybody, but the image managed to capture the imagination of all who saw it, and it took on a life and meaning of its own."
He and his Cornell colleagues followed up the nanoguitar with a nanoharp. The researchers make silicon rods vibrate by applying a radio frequency voltage signal through the silicon base. They then measure the resulting vibrations by bouncing laser light off the strings and observing the reflected light with a sensitive interferometer. As with a full-size harp, the resonant frequency at which one of these tiny strings vibrates depends on the length and the mass. However, Carr said, these microscopic strings are not under tension like those in a musical instrument and the resonant frequency of the nanoharp's strings follows a different rule, varying as the square of the length, like a metal bar struck by a hammer. "It's really more like a xylophone than a harp," he said.

In September 2004 Carr was selected by the Massachusetts Institute of Technology's Technology Review as one of the year's top 100 researchers under the age of 35. Says Terry Michalske, Sandia's Center for Integrated Nanotechnologies (CINT) program director, "I was very pleased when Dustin contacted me about his interest in joining Sandia and getting involved in CINT. I've admired his work for a long time. He has pushed the limits to build some very important nanoscale structures."
The future for this young scientist is bright and he could certainly pursue any field of study that intrigued him. He says that sensors technology is the most interesting area for him now. According to Carr, "The idea of gathering information in ways that can be put to good use is a fundamentally positive thing for so many areas of life. Mankind is entering into a new era where we do not merely try to fix things as they break, but we seek to understand better just how things work when they are not broken. This applies to the human body as well as the earth, the environment and man-made constructs. I am developing sensors that utilize light for detecting very slight amounts of motion. This is something that has been enabled by the advancements in optical technologies, especially telecommunications and optical data storage. It is an idea whose time has come and this group at Sandia is leading something that could be quite revolutionary in many sensor fields. This project is on the leading edge of science and applications, and that is where I like to be."

—€”Margaret Lovell