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CWRU researchers create electronic nose to detect hazards

Case Western Reserve University : 12 January, 2003  (Technical Article)
Case Western Reserve University physicists and engineers are designing an 'electronic nose' that will sniff out, without sounding an alarm, nerve gas and other chemicals used in warfare or terrorism.
The new 'nose' is a hologram-like patch that utilizes liquid crystals and can be worn by individuals going into hazardous areas, or it can be attached to planes flying over combat zones. Instead of an alarm sounding like with some other detection devices, a pattern appears on the patch when a chemical hazard is present.

According to Rolfe Petschek, professor of physics, who came up with the idea for the sensor, when a hazardous molecule attaches itself to a chemical-specific molecular sensor in the polymer and liquid crystal matrix of the electronic nose, the elongated liquid crystal molecules align in a new pattern, changing how light moves on the patch. The resulting pattern is similar to pictures on credit cards, CDs and certain games with finely striated plastic surfaces that have several pictures that change as the direction of the light changes. For the sensor, the pictures only appear when a chemical hazard is present.

Other 'electronic noses' are currently available, and more are being designed. According to Petschek, the CWRU version, which has been under development for the past year, more easily and naturally solves the problem of distinguishing between unimportant changes in the environment, such as temperature, and the presence of specific hazards. Other sensors also give off many false positives or false negatives, he said.

Petschek has received funding from the U.S. Air Force to develop the sensor. The project evolved from the fundamental research of Charles Rosenblatt, also a professor of physics, who has undertaken the study of the science behind the sensor. His research has the support of a three-year, $340,000 grant from the Department of Energy's nanotechnology program. Petschek and Rosenblatt, along with Stuart Rowan, assistant professor of macromolecular science, are creating the technology. The chemical sensors designed by Rowan are attached to the device's polymer surface using techniques developed by Rosenblatt in a pattern created by Petschek.

Petschek's work relates to the science research Rosenblatt conducts on the atomic force microscope. The AFM was designed to read surface shapes by running a sharp silicon tip one-10,000th of a width of a human hair above the surface. Rosenblatt says it reminds him of the old-style needles on records player, but on a much tinier scale.

Several years ago, Rosenblatt expanded the microscope's operations from a reading to a writing tool. Like a feather quill, the AFM needle inscribes patterns on the polymer surface with pixels as small as one-2000th the width of a human hair. When placed in contact with the surface, the liquid crystal molecules align along the pattern. Milind Mahajan and Bing Wen, CWRU graduate students, have designed computer programs that direct the etching through a mechanical rubbing process.Rosenblatt has five provisional patents pending for his patterning work.

Rosenblatt also has teamed up to use the technique for development of optical communication devices and liquid crystal displays used in laptop computers and in flat-panel desktop monitors. During the past 22 months, he has received grants from DOE, NASA and NSF totaling $1.06 million for work in this area and others.
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