Musical instrument-like sensor detects fake medicine

A low-tech sensor based on sound frequencies could provide an affordable way to detect counterfeit and adulterated drugs.

The device – built by an engineer at the University of California Riverside – can be used to identify substances based on the density of the liquid. The idea behind the research is that comparing the density of a suspicious liquid medicine to the density of the same confirmed product can determine whether the medicines are made of the same components.

The inspiration for the research was based off the fact that frequencies of sound created by an instrument are determined by the physical properties of the instrument; as an example, the length and tension of a guitar string affects the pitch of a note.

William Grover, an assistant professor of bioengineering at UCR’s Marlan and Rosemary Bourns College of Engineering asked, “could we add a sample to a musical instrument, measure the result change in the instrument’s notes, and use this change to determine information about the sample and its properties?”

Grover and his team modified a mbira, a musical instrument originating in Africa made of metal prongs attached to a soundboard. The prongs play different notes when plucked with a finger, but when the prongs were replaced with a length of metal tubing and filled with a liquid, Grover could compare the frequency of the musical notes made by the instrument when the tube was either full or empty, to measure the liquid’s density. Empty, the tube played a G sharp note, and when filled with water, it played an F sharp note.

The optimum mbira sensor tube had thin walls, and a length no shorter than 50 millimetres, and Grover’s students measured the density of as many different liquids as they could, but eventually settled on detecting dangerous medicines as the first application for their sensor. Crucially, the device can be constructed from off-the-shelf or discarded materials, sidestepping the need for expensive equipment used by expert technicians.  They have published their work in the journal ACS Omega.

One notorious addition to counterfeit cold medicines is diethylene glycol which can be easily mistaken for glycerol, an excipient commonly used in many cold and flue medicines. An inexpensive sensor to differentiate between the two could save lives, as DEG is a poison that has caused many people to die – most recently causing the death of at least 84 Nigerian children between ages of two months and seven years in 2008 who ingested it in teething syrup.

The researchers calibrated the sensor to make sure it could tell the difference between glycerol and DEG, a difference of 10 hertz when analysed with a website created for this specific experiment. This difference is too small to be noticed by ear, but someone using the mbira sensor and a smartphone could distinguish between the two using the software.

Once the sensor had been calibrated, the researchers tested six different batches of a common cold and flu medicine collected from different pharmacies in the surrounding area. All samples made the same musical note when loaded into the sensor, which suggests all the samples were authentic and identical, and any sample making a different note must be different chemically and therefore counterfeit.