A sensor inspired by an African thumb piano could root out bogus medicines

Identifying faulty drugs or diagnosing kidney problems could one day be as simple as playing an instrument and analyzing the sound.

An inexpensive, handheld tool inspired by an ancient African instrument called an mbira, or thumb piano, can distinguish between liquids of different densities, researchers report online September 12 in ACS Omega. That could help pharmacists and consumers identify counterfeit and contaminated drugs, which make up an estimated 10.5 percent of all medications in low- and middle-income countries.

Bioengineer William Grover built his first mbira-inspired sensor with his 8-year-old son. “It probably took about 30 minutes,” using scrap materials they had around the house, says Grover, of the University of California, Riverside. The duo kept the instrument’s wooden sounding board design, but swapped out the row of metal prongs that play different notes for a hollow, U-shaped metal tube, where the liquid is placed.

Plucking the tube when it’s filled with viscous liquids produces lower frequency notes. Thinner liquids produce higher pitches. A user can upload audio recordings from the sensor to a website that analyzes the sound frequencies to discern differences too subtle to hear. Comparing the density of a suspect liquid with that of a known, authentic sample can reveal whether the two substances are the same.

Grover’s team tested whether the device could differentiate between glycerol, a sweet syrup common in cough medicine, and a similar but poisonous syrup called diethylene glycol that has been mistaken by drug manufacturers for glycerol — with deadly consequences (SN: 6/18/11, p. 22). When the mbira sensor was filled with glycerol, it played notes about 10 hertz lower than when filled with diethylene glycol.

The device can also measure the specific gravity of fluids — that is, their density compared with that of water. Field clinics could use the device, for example, to test the concentration of urine samples for signs of dehydration or kidney problems. Brewers could test the specific gravity of fermenting alcohol products to keep track of the declining sugar content and increasing alcohol content. 

Already, south Indian villagers have begun using the device, after UC Riverside bioengineer Vamsi Choday in January shared several sensors with people in his grandparents’ hometown of Valluru. Choday’s mother, for instance, used one to measure the fat content of bison milk to help keep tabs on the animals’ health.