New electrical technique for painless, non-invasive blood glucose tests

Quick, painless ways to measure blood glucose levels are important for monitoring diabetes as well as a number of other medical conditions. In the conventional approach, blood is drawn from the body, usually with a pinprick, but since this sometimes must be done multiple times a day, noninvasive techniques are greatly desirable. Spectroscopic methods have been tried, but these often suffer from low accuracy and unreliability.

In a recent paper, investigators report on the development of a new type of noninvasive glucose monitoring technique based on low frequency capacitive measurements. The sensing capacitor consists of a curved copper plate wrapped around a silicon tube of suitable length and diameter to receive a patient’s finger. Because the finger is essentially an aqueous glucose solution, it serves as a dielectric. An identical copper plate and silicon tube system serves as a dummy capacitor with air as its dielectric. Both are connected to a simple electronic circuit with an LCD calibrated to display glucose concentration. A sinusoidal voltage is used as input to the circuit.

The investigators found that the ratio of output to input voltage varied linearly with glucose concentration. While capacitance varies with humidity and temperature, these effects are negligible since they cancel out when the ratio of input voltage to output voltage is taken.

The three middle fingers of eight individuals were studied. Readings from a commercial glucose meter taken at the same time were almost identical to readings with this new device, which had a measurement error of 3.5%.

This approach holds promise for a quick, painless way to monitor blood glucose levels.

Source: “A non-invasive microcontroller based estimation of blood glucose concentration by using a modified capacitive sensor at low frequency,” by Abhinaba Dutta, Satish Chandra Bera, and Kamalesh Das, AIP Advances (2019) The article can be accessed at https://doi.org/10.1063/1.5116059 .