Electric-paper sensors could replace diabetic finger-pokes
There may soon be yet another alternative to the painful finger-prick blood glucose tests which diabetics have to endure on a daily basis. Scientists in Saudi Arabia have developed a paper-strip sensor that gauges blood glucose via a patient's saliva.
The project is being led by bioscientist Sahika Inal, electrical engineer Khaled Salama and materials scientist Derya Baran, all from the King Abdullah University of Science and Technology.
They started by loading an inkjet printer with a commercial ink containing electrically-conductive polymers, and then proceeded to print microscale electrode patterns onto glossy strips of paper, using that ink. Next, over top of the electrodes, they printed a layer of an enzyme known as glucose oxidase. Finally, they coated the whole thing with a nafion polymer membrane.
When saliva was subsequently applied to the sensor, glucose present in the body fluid reacted with the glucose oxidase, creating an electrical signal. That signal was picked up by the electrodes, and could be read by a separate device – the strength of the signal corresponded to the blood glucose levels of the person who supplied the saliva.
That said, saliva does contain substances like ascorbic acid, which ordinarily would electrically interfere with the conducting polymers. The nafion membrane kept that from happening, however, as it repelled the negative electrical charges produced by such compounds. That membrane also boosted the shelf life of the sensor, allowing the glucose oxidase to still be active after being stored for a month in a sealed bag.
"Optimization never ends in engineering, so we are trying to make this system more robust to detect other metabolites in biofluids," says Inal. "We are also looking to integrate printed and self-powered energy devices into the sensors, giving us a more user-friendly platform that eliminates external batteries or wires."
A paper on the research was recently published in the journal Flexible Electronics.