The researchers at the Fraunhofer Institute for Microelectronic Circuits and Systems (IMS) in Duisburg worked with Dutch medical firm Noviosens to produce a low power biosensor for blood glucose that combines measurement and digital analysis with both an RF link and can be powered by RF energy in the environment.

For many diabetics checking blood glucose is an everyday part of life, especially for patients with Type-1 diabetes who always have to keep a close eye on their levels as their bodies are incapable of producing the insulin to break down the glucose in the blood. Several times a day, they have to place a tiny drop of blood on a test strip. It is the only way they can ascertain the blood glucose value, so they can inject the correct amount of insulin needed. And this pricking is not only a burdensome: it may also cause inflammation or cornification of the skin.

The biosensor avoids this as it is located on the patient’s body and is able to measure glucose levels continuously using tissue fluids other than blood, such as in sweat or tears.

The measurement involves an electrochemical reaction that is activated with the aid of an enzyme. Glucose oxidase converts glucose into hydrogen peroxide (H₂O₂) and other chemicals whose concentration can be measured with a potentiostat and this measurement is used for calculating the glucose level.

The 0.5 x 2.0 mm chip includes the nanopotentiostat and the diagnostic system. “It even has an integrated analog digital converter that converts the electrochemical signals into digital data,” said Tom Zimmermann, business unit manager at IMS. The biosensor transmits the data via a wireless interface, for example to a mobile receiver. Thus, the patient can keep a steady eye on his or her glucose level. “In the past, you used to need a circuit board the size of a half-sheet of paper,” says Zimmermann. “And you also had to have a driver. But even these things are no longer necessary with our new sensor.”

Earlier systems required about 500 µA at 5 V; now, it is less than 100 µA. That increases the durability of the system – allowing the patient to wear the sensor for weeks, or even months. The sensor is able to send and receive data packages, but it can also be supplied with power through radio frequency.

The next stage is to look at using the biochip to control an implanted miniature pump that, based on the glucose value measured, indicates the precise amount of insulin to administer. That way, diabetes patients could say goodbye to incessant needle-pricks forever.

www.ims.fraunhofer.de