The University of Texas at Austin

Researchers taste success with electronic tongue

     While artists may complain that critics' taste exist only in their mouths, UT engineers and scientists have now successfully placed it on a silicon chip.

     Using chemical sensors, these UT researchers designed an electronic tongue that mimics the real thing. Like its natural counterpart, it has the potential to someday distinguish between a dazzling array of subtle flavors using a combination of the four elements of taste: sweet, sour, salt and bitter. And in some ways it has outdone Mother Nature: it has the capacity to analyze the chemical composition of a substance as well.

     The device, which has the potential to incorporate hundreds of chemical microsensors on a silicon wafer, has a multitude of potential uses. The food and beverage industry wants to develop it for rapid testing of new food and drink products for comparison with a computer library of tastes proven popular with consumers.

     But the artificial tongue can also be used for more distasteful purposes, to analyze cholesterol levels in blood, for instance, or cocaine in urine, or toxins in water. The National Institutes of Health recently gave the UT group $600,000 to develop a tongue version to replace the multiple medical tests done on blood and urine with one fast test.

     The tongue research, reported this summer in the Journal of the American Chemical Society and in the British magazine New Scientist, began in 1996 when electrical and computer engineering professor Dean Neikirk and chemists John McDevitt  and Eric Anslyn began casual discussion of the idea. Neikirk and McDevitt had already designed a nose to sniff out iodine, but soon realized that many chemicals don't evaporate. The new collaboration incorporated the work of Anslyn, a UT chemist and tongue researcher, who uses polymer microbeads to synthesize DNA and its proteins.

     The team attached four well-known chemical sensors to Anslyn's minute beads and placed the beads in Neikirk's micro-machined wells on a silicon wafer. Like a human tongue, the wells mimicked the tongue's many cavities that hold chemical receptors known as taste buds. Each bead, like a tongue's receptor, had a sensor that responded to a specific chemical by changing color. One turned yellow in response to high acidity, purple under basic conditions. Then the researchers read the sensor's results through an attached camera-on-a-chip connected to a computer.

     The sensors responded to different combinations of the four artificial taste elements with unique combinations of red, green and blue, enabling the device to analyze for several different chemical components simultaneously. This is where the group employed the expertise of chemist Jason Shear, who developed the dye photochemistry.

     “The most pleasant aspect of our work has been the really neat way the expertise of the various team members has meshed. We have each been able to bring to the project something that might seem easy to one person, but is simply not possible for another,” muses Neikirk. “This has been a great example of how science and engineering can work together to produce something that will hopefully be of real utility.”

     From the silicon tongue, the team hopes to create a process to make artificial tongues more cheaply and quickly, placing them on a roll of tape, for example, to be used once and thrown away, explained Neikirk.

     “Surpisingly this technology has created interest in vastly different areas,” says McDevitt. “Besides the food industry, environmental and tourist industries want to incorporate it into hand-held monitors for feedback about local air and water. And there are huge markets in biomedical applications.”

     The researchers submitted a series of scientific publications demonstrating the use of their artificial tongue and have applied for several patents.