Researchers Develop Optical Nose

Two California professors have started a company to develop and manufacture an electronic nose, capable of sniffing out traces of volatile chemicals in the air. They foresee their invention of an optical nose will have applications in detecting drugs and explosives at checkpoints using handheld devices, and be able to detect a mere handful of molecules floating in the air.

Juan Santiago, associate professor of mechanical engineering at Stanford University, and Carl Meinhart, associate professor of mechanical and environmental engineering at the University of California Santa Barbara, were attending a conference in England when the pair began discussing their common interest in applying spectroscopy to microflows of fluids. Santiago mused on what could be accomplished if they could expose a miniature stream of water to air in a real world environment and measuring what dissolved in it, when Meinhart told him he knew how. Santiago says the pair have known each other for 11 years, since his days as a graduate school in the 1990s at the University of Illinois.

Santiago and Meinhart both study Raman spectroscopy in flows of liquids pushed through fibers must microns thick. With Raman spectroscopy, a laser is flashed onto either a fluid or solid surface, and the reflected spectrums measured by a sensor. Every molecule has a unique 'signature,' and detectors to analyze and report on the reflected laser light have been developed by Meinhart and others that are just an inch in size.

One of Meinhart's areas of research includes development of such MEMS chips. MEMS stands for Micro-Electro-Mechanical Systems, and are 'smart' chips capable of detection, analysis, and reporting functions, as well as triggering other actions within a device. A breakthrough in MEMS technology being powered using lasers was announced less than two weeks ago at the Massachusetts Institute of Technology.

The method employed by Meinhart and Santiago puts small bits of gold or silver in the flow of water, and applying a charge to the water, and an opposite charge to the tube in which it is flowing, causing the two to repel each other. Additionally, the tubing is made from materials known as hydrophobic, which naturally repel water from their surfaces, as well as the natural hydrostatic property of water that causes beads to form on a glass tabletop.

By putting gold or silver in the water, molecules that make up such organic compounds as cocaine or explosives aggregate on the surface of the metal, concentrating them on a surface from which the laser will reflect.

Their new company SpectraFluidics has applied for patents on the technology. Their paper ""Microfluidic Control of Nanoparticle Aggregation for Surfaced Enhanced Raman Spectroscopy" will be published Proceedings of the National Academy of Sciences. Other authors of the paper include Brian D. Piorek, Seung Joon Lee, Martin Moskovits and Sanjoy Banerjee of UC-Santa Barbara.

In a press release from Stanford, Meinhart says "We're using light to smell things only your dog can smell."