Artificial nose senses odor by seeing colors.

Imagine a small slip of paper that can sniff out odors, such as sour milk or toxins, by simply changing its color. Chemists at the University of Illinois (School of Chemical Sciences, Chemical and Life Science Building, Room A422, 600 S. Mathews, Urbana, IL 61801) have developed an artificial nose that works by visualizing colors. About three months ago they applied for a patent covering their smell-seeing technology, which should be available for licensing once the patent issues. The researchers have proven the technology and are interested in collaborating with industry or testing the technology at commercial sites. Eventually, a commercial device might be a hand-held unit.

Smell-seeing arrays have many potential applications, such as to detect the presence of flavorings and additives, or if a product spoils. Unlike other technologies used in artificial noses, smell-seeing is not affected by changes in relative humidity. The color-change technique is extremely insensitive to water vapor. The ability to easily detect odors regardless of humidity levels is a big advantage of the technology. The nose functions by analyzing changes in colors that occur in an array of vapor-sensitive dyes known as metalloporphyrins, which are doughnut-shaped molecules that bind metal atoms. These molecules are closely related to hemoglobin and chlorophyll. The technique is similar to using litmus paper to determine if a solution is acidic by seeing if the paper changes from blue to pink. But scientists have generalized the process so that a whole range of chemical properties is being screened by an array of many different types of dyes that change color when they interact with various chemicals. The resulting changes in the array provide a color fingerprint that is unique to each vapor.

To create an array, the researchers paint a series of dots--each dot is a different dye--on an inert backing, such as paper, plastic or glass. The array is then scanned with an ordinary flatbed scanner or an inexpensive electronic camera before and after its exposure to an odor-producing substance. By subtracting the "before" image from the "after" image, researchers obtain the color-change pattern of the odorant.

Meanwhile, Australian investigators have built a more-traditional electronic nose that assesses the quality of olive oils and checks for contaminants. Research at the University of Wollongong involves developing of more-processable polymers and fabricating inexpensive sensors from these materials. Researchers are able to process water-soluble polymers, organic solubles and water-based dispersions at the 50 g to 100 g level. Many of these can be used to fabricate simple sensors using screen printing or ink-jet printing techniques. New applications will require the design and development of new polymers.

One of the most significant improvements in the food industry during the next few years is likely to be the development of intelligent processing systems incorporating automated and rapid chemical analysis. Many scientists are interested in working with industry to develop new sensing arrays for specific applications.

Further information. Kenneth Suslick; phone: [phone]; fax: [phone]; email: [e-mail]. In Australia: Joseph N. Barisci, Intelligent Polymer Research Institute, University of Wollongong, NSW 2522, Australia. Phone: [phone]. Fax: [phone]. email: [e-mail].