An acoustic nose

Used to precisely determine the chemical makeup of a vapor, was demonstrated at the Acoustical Society of America meeting last December in Newport Beach, California. In the device, a flowing stream of helium gas carries the vapor of interest through a heated, specially coated meter-long gas chromatography column, in which the vapor’s constituent atoms and molecules are segregated by mass, and all similar atoms or molecules travel together. The various species then fall sequentially on a 500-MHz surface acoustic wave resonator, where they rapidly condense—a hallmark of a vapor—and are then evaporated, making room for the next arrival. The arrival time at the sensor identifies the species by mass, and the total mass of that species alters the resonator’s frequency, thereby yielding the concentration. Concentrations as low as parts per billion (or trillion in some cases) were detected. Created by Edward Staples (Electronic Sensor Technology, Newbury Park, California), the zNose™ can analyze a vapor with hundreds of different species in 10 s. Staples anticipates many uses, including in the food and beverage industry, forensics, and environmental science.