Bioengineers have developed a Band-Aid-sized glucose monitor that could transform the way diabetics monitor their blood sugar.

The wearable device can detect blood sugar through minute amounts of perspiration on skin. The micromonitor can do its job using about as much sweat as would fit in a cube the size of one salt crystal.

To ensure that such a tiny amount of sweat would generate a strong enough signal, Shalini Prasad, professor of bioengineering in the Erik Jonsson School of Engineering and Computer Science, in Richardson, Texas, and her researchers demonstrated the capabilities of a biosensor they designed to reliably detect and quantify glucose in human sweat.

Prasad said that researchers who work with sweat often use a process called iontophoresis, which sends an electric current through the skin to generate enough perspiration for sensing experiments. But because this method can lead to rashes and even burns on the skin, the team sought an alternative that would work with small amounts of sweat.

So they started by modifying the surface of the an off-the-shelf material. "We used known properties of textiles and weaves in our design," Prasad said. "What was innovative was the way we incorporated and positioned the electrodes onto this textile in such a way that allows a very small volume of sweat to spread effectively through the surface."

"Our modifications allow this material to entrap glucose oxidase molecules, which effectively amplifies the signal," Prasad said.

She and her colleagues also were able to account for the fact that the chemistry of a person's sweat changes throughout the day. "Glucose is a tricky molecule to monitor because other factors can confound a signal," Prasad said. "For example, the pH, or acidity, of your sweat can vary greatly depending on the circumstances." She noted that when individuals exercise or are under stress, other compounds in their sweat — including cortisol and lactic acid — change as well, which could hinder glucose detection.

Prasad said her team had overcome these obstacles with their monitor: "We have shown that with our technology, we address three critical issues: low volume of ambient sweat, interference from other compounds, and pH swings."

Prasad tested their prototype using samples of human sweat from donors. The technology provides a real-time response in the form of a digital readout.

While the micromonitor is still a few years away from hitting store shelves, it should be easily commercialized and easily scalable.

"At this point, we are thinking of this sensor as something you use for a day and toss out, and we believe it could easily be incorporated into existing consumer electronics platforms," Prasad said. She and her colleagues published their announcement in the journal Sensors and Actuators B: Chemical.

Cases of diabetes are exploding in the United States. The Centers for Disease Control and Prevention estimates that 29 million people in the United States have diabetes and 86 million have prediabetes — a condition that tends to develop into diabetes.