The Wire @ WPI Online
VOLUME 13, NO. 2     NOVEMBER 2000

Studying the world's tiniest machines

Imagine a machine so small it can travel through your bloodstream to fix a clogged artery. Imagine one so smart that when its job is complete, it shuts itself off and is eliminated from the body. Imagine that same technology at work in myriad applications, from automobile airbags to computer security.

These and hundreds of other futuristic visions are the products of the emerging field of nanotechnology.

Nano means something exceedingly small, and the products of nanotechnology are small, indeed: microgears and tiny engines with diameters comparable to the width of a human hair. Under the direction of Ryszard J. Pryputniewicz, professor of mechanical engineering and director of the Center for Holographic Studies and Laser micro-mechaTronics (CHSLT), WPI has moved into the study of these tiny devices in a big way.

Working closely with research assistant professors Cosme Furlong and Gordon C. Brown, Pryputniewicz has made fundamental contributions to efforts to measure and study the workings of nanomachines, many of which can be viewed only under a powerful microscope and some of which have gears that spin at incredible speeds (a million revolutions or more per minute).

"We specialize in test measurement and optimization," Pryputniewicz says. "We seem to be the only people in the world who can work at this level." And unlike other research laboratories working in this emerging discipline, Pryputniewicz notes, CHSLT is able to measure critical characteristics of nanomachines, including speed and deformation, in real time and in the full field of view. (While other teams measure individual points on a microstructure and compile them to create an image of the whole unit, the WPI lab measures the entire structure in a single operation.) The machines tested at WPI are developed by industry and national laboratories, particularly Sandia National Laboratories in New Mexico, science-based engineering labs funded by the U.S. Department of Energy and managed by Lockheed Martin. The devices are made with the same masking, etching and deposition techniques that are used in industry to fabricate integrated circuits, which makes it possible to manufacture them in large quantities.

When they arrive at WPI, the machines are examined with variations of laser holographic techniques and other sophisticated measurement tools that Pryputniewicz has fine-tuned over the course of more than two decades. For the studies of the micromachines, the lab has been using laser optoelectronic interferometry, a technique that makes it possible to record and process data in real time from stationary or moving objects, setting a new standard for quantitative holographic analysis, Pryputniewicz says.

With these techniques, the WPI lab is able to see how the parts of the machines deform under load and spot problems, such as unbalanced parts, misaligned gears or excess friction, that can shorten their operating life.

Helping research labs develop efficient and reliable nanomachines that can be mass-produced at a reasonable cost will open the door to a wide range of new applications limited only by scientists' imaginations. "Eventually you will have an entire laboratory on a chip," Pryputniewicz says. "It will be able to measure position, velocity, acceleration, elevation, orientation, chemistry, or whether something is environmentally safe. Nanomachines may be used instead of passwords for computer security. They'll be in everything from smart sensors to airplane guidance systems to a new generation of biomedical devices that may repair the body, help paraplegics walk, and enable the blind to see. The possibilities are endless."

For more information on nanotechnology, visit the WPI Web site,, or the Sandia Web site,

Above, the first image is a photomicrograph of a gear from a microengine. The smaller gear is approximately 30 microns across. WPI's research team used laser interferometry to detect wobble in the gears as they were spinning at 360,000 RPMs. Wobble causes decreased gear life. The fringes in the second photo indicate that the gear is tilting. The pacing of the fringes shows the degree of tilt; the direction of the fringe lines runs perpendicular to the direction of tilt.

Professor of Mechanical Engineering Ryszard J. Pryputniewicz (better known as Dr. P), standing, works in close collaboration with Professor Gordon C. Brown in the Nanoindenter Lab, part of WPI's Center for Holographic Studies and Laser micro-mechaTronics (CHSLT), where researchers are studying machines so small they can only be seen through a powerful microscope.

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Last modified: Dec 11, 2000, 16:34 EST