Photo of page of sensors.
A page of sensors made from conducting plastics and living enzymes. (Credit: Eloïse Bihar)

A technique that enables biologically active enzymes to survive the rigors of inkjet printing presents a promising alternative to routine blood screening exams faced by diabetic patients. A team of researchers used this approach to make disposable devices that can measure glucose concentrations in human saliva.

Strips of pH-sensitive paper are commonly used to test whether a liquid is acidic or alkaline. Researchers are now working to apply similar principles to create paper sensors that quickly indicate disease biomarkers. Key to this approach is replacing traditional electronic circuitry in the sensors with low-cost plastics that can be manufactured quickly and in large quantities.

The researchers used inkjet technology to produce sensors sensitive to small sugar concentrations in biofluids. Using a commercial ink made from conducting polymers, the team printed microscale electrode patterns onto glossy paper sheets. Next, they printed a sensing layer containing an enzyme, glucose oxidase, on top of the tiny electrodes. The biochemical reaction between available glucose and the enzyme creates electrical signals easily correlated to blood sugar levels.