A team led by Kenneth Suslick, a professor at the University of Illinois at Urbana-Champaign, built a postage stamp-sized sensor made of paper dotted with colored pigments.
Using an eyedropper, the team soaks the “tongue” with a test liquid. By scanning the array of dots with a computer before and after wetting the sensor, the team was able to discern how that liquid “tasted.”
In this case, taste is sweetness, one of five distinct flavor sensations, along with saltiness, sourness, bitterness and savoriness.
After running dozens of samples of artificial sweeteners dissolved in water or tea, the research team reported that the “tongue” could pick out which sweetener was used with 100 percent accuracy.
Like our own sense of taste or smell, the array only works collectively, and no single dot on the “tongue” — which is made of a tiny gel coated with a pigment that reacts to different sweeteners — can detect any single sugar or sugar substitute.
To date, “sourness” — or acidity — can be tested with litmus paper, and “savoriness” and “saltiness” can be measured by handheld devices sensitive to protein levels and sodium and potassium ions.
“Bitterness” remains a biochemical mystery.
In a National Geographic article, Suslick said the electronic “tongue” could eventually be put to use as a breathalyzer for detecting harmful bacteria or as a way of detecting early warning of diseases such as pneumonia and lung cancer.
The sensor can also be used by food processors, who currently use a slow, expensive and laborious test called “high-pressure liquid chromatography” to measure sweeteners on the assembly line for quality control. In contrast, Suslick’s “tongue” is small, inexpensive, disposable, and speedy, producing results in just two minutes.
The study appeared in the journal Analytical Chemistry.