Raman devices work by shooting a laser beam at an object. The laser light interacts with the object’s electrons, making the atoms vibrate and shifting the energy of the laser photons up or down. The shift creates a visual pattern—the Raman effect, named after C. V. Raman, the Indian scientist who discovered it in the 1920s. Almost every material has its own unique Raman pattern, based on how strongly its atoms are bonded.
Raman, who won a Nobel Prize for his discovery, realized that this scattering of light offered an alternative to X-ray diffraction as a means of identifying compounds. But not until the advent of more powerful, less expensive lasers in the 1970s and ’80s and advances in digital imaging in the 1990s, spurred by NASA and the telecommunications industry, did scientists begin researching applications for Raman spectroscopy.
At about the same time, Richard Van Duyne, a chemistry professor at Northwestern University, found that the intensity of the Raman signal was proportional to the electromagnetic field on the surface of an object, and that enhancing the electromagnetic field with gold or silver or copper would boost the Raman signal considerably. In fact, a device using “surface-enhanced Raman spectroscopy” can detect traces of less than one part per billion. As a result, it can be used to identify minute quantities of explosives in liquids or deadly bacteria on a table in a meatpacking plant. Rick Cox, the head of business development at DeltaNu, estimates that while Raman technology is now a $150 million business, within five to 10 years, handheld Raman instruments selling for less than $5,000 will be available to everybody to identify just about anything.
The potential medical applications of Raman technology are perhaps the most exciting. Researchers at Stanford University are experimenting with it as a non-invasive tool to diagnose breast, lung, and other cancers. River Diagnostics, in Rotterdam, is marketing a bacteria-strain analyzer to identify pathogens in real time and combat hospital-acquired infections. Diabetics may someday be able to monitor their glucose without poking themselves to get a drop of blood. Allergy sufferers may be able to instantly detect which pesky pollens are in the air and respond accordingly.
But to identify materials, you need databases of Raman patterns. “We are in the midst of another tremendous era of reclassification—like the scientists of the 18th century,” says Robert Downs, a mineralogist who with his University of Arizona colleague Bonner Denton, a chemist, has spearheaded the development of Raman technology.
Over the past five years, Downs and his team have identified the Raman patterns of about half the Earth’s 4,000 minerals. So far, other scientists have generally been willing to share their knowledge, but Downs is troubled by the prospect of companies’ putting exorbitant user fees on their databases. “The Raman effect is part of the innate quality of matter—like DNA,” he told me. “No one owns the song of a bird.”