Invention has impact beyond the lab

By Steven Schultz

Princeton NJ -- The scientific world is full of instruments that measure, count, weigh and otherwise detect physical things with a level of precision that is hard for non-scientists to appreciate. Every once in while, however, a device comes along that is so much more sensitive than anything else it puts even the most advanced tools to shame and creates commercial opportunities that extend far beyond the laboratory.

A device developed by Kevin Lehmann, professor of chemistry, to detect traces of gas is listed among the top 100 inventions of the year by R&D Magazine.


That is the category into which an innovation by Princeton chemist Kevin Lehmann fits. He has invented a device that detects traces of gas with a combination of sensitivity, precision and speed that is far greater than any other technology. More than just a technical feat, his invention stands to become a valuable resource for a number of industries, including computer chip manufacturers, which require extraordinarily pristine conditions.

Princeton has patented Lehmann's invention and licensed it to an instrumentation company that started to market it earlier this year. This summer, the Research and Development Council of New Jersey awarded Princeton and Lehmann its Thomas Edison Patent Award and, in September, R&D Magazine listed it among the top 100 inventions of the year.

Lehmann's patent also has the distinction of being the first at Princeton to be developed into a marketed product, said John Ritter, director of technology licensing and intellectual property. While many Princeton discoveries have been patented and licensed to companies, all but Lehmann's are still under development.

"It's not an incremental improvement on any technology," said Roger Van Zee, an expert in gas measurements at the National Institute for Standards and Technology. "It really just outstrips everything else."

Lehmann's invention, called continuous wave cavity ring-down spectroscopy, can detect the presence of gasses down to the level of a couple hundred parts-per-trillion. That is like pointing a detector at the earth and being able to tell in a matter of milliseconds whether the world population has gone up or down by a single person.

Lehmann began working on the idea in 1994 when his graduate student Daniele Romanini found and began working with commercially available mirrors with extremely efficient reflection of light. Lehmann realized that these high-tech mirrors would allow him to bounce light back and forth in a box for a very long time with very little loss, and that this ability could be the key to detecting trace gasses.

Scientists detect gasses by shining a light through them and looking for changes in the color; different gasses absorb different bits of the light spectrum, creating a unique signature. This technique, called spectroscopy, works best when there is plenty of gas to detect; trace amounts do not absorb enough light to be detected. Lehmann realized that he could boost the absorption by passing the light through the gas many times.

Upon looking into it further, Lehmann found that others had worked on similar ideas, but none had proven practical outside carefully controlled laboratory settings. One problem was that these early efforts used expensive, bulky and temperamental research-grade lasers as the source of light. Through a unique combination of theoretical calculations and experimental innovations, Lehmann found that he could use an off-the-shelf laser similar to those commonly used in CD players and other commercial devices.

"It's harder to do, but in the end it makes the system more stable," said Lehmann.

The University immediately applied for and received a patent. In 2000, Princeton licensed it to the instrumentation company MEECO Inc., which formed a spinoff company, Tiger Optics, to market the device. The first device on the market detects water vapor, which is of particular concern to semiconductor manufacturers.

Lehmann now has two more patents, one with Paul Rabinowitz, a visiting research collaborator, and another with Rabinowitz and Peter Tarsa, a graduate student, to expand the range of substances that can be detected and possibly to detect minute impurities in liquids as well as gasses.

These inventions could be useful in an even broader range of areas, from medicine to national defense. In medicine, doctors could diagnose illnesses such as diabetes or asthma by examining the composition of gasses in the breath of patients. In national defense, the devices possibly could be used to detect chemical and biological warfare agents.

For Lehmann, work on these devices has been a nice change of pace from the basic research that occupies the majority of his time, the investigation of the fundamental physics of chemical bonds. "It wasn't just 'hand over the idea and here's a product,'" he said. "There were a lot of technical problems that we were involved in solving."

His work on those problems, in turn, promises to open new avenues for his basic research, a mixture he finds appealing. "I have been very excited about being able to solve real-world problems that have an impact on many people," he said.

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