Georgetown College. Georgetown University.

A daily regimen of pricked fingers and blood tests is an essential part of life for someone living with diabetes.

Monitoring blood glucose levels can be tiresome, even with today’s improved monitoring devices. Drs. Mak Paranjape and John Currie, researchers in the Georgetown Advanced Electronics Laboratory (GAEL), are working to take the process to a whole new level.

For the past few years, the team has been developing and testing a new biosensor device for blood glucose monitoring. The size of a small bandaid, it is designed to be worn anywhere on the body, where the biosensor samples tiny amounts of fluids that lie just beneath the skin. The device is small and convenient, and makes measuring glucose levels pain-free and noninvasive.

How is this device possible on such a small scale without puncturing the skin? Imagine the human skin as if it were a large frozen body of water, like the Tidal Basin in Washington DC, in December. Under the top layer of thin ice would be water, just like the glucose-rich interstitial fluids just underneath the skin. Traditional blood monitoring uses a needle to make a (relatively) large, deep hole to extract blood droplets from the capillaries, which lie deeper under the skin surface. In the analogy with the frozen Tidal Basin, the blood vessels would lie on the bottom of the lake. The needle in this device might be analogous to the Washington Monument, creating a very large hole through the ice. Painful, indeed!

The new bio-sensor, however, makes possible a different, painless approach. Instead of puncturing a “big” hole into the skin, the bio-sensor works by making tiny pores in the skin, through which the interstitial fluid can rise. This would be similar to melting a very small region in the ice to access the water below.

The biosensor device works to painlessly remove this outer-dermis, or dead-skin layer, by using a “micro-hotplate” (or micro-heater), which measures about 50 microns square and is carefully controlled to apply a small amount of power. (To imagine how small this area is, note that the period at the end of this sentence is about 10 times larger than the hotplate). For 30 milliseconds (that’s 30 one-thousandths of a second) the “hotplate” is turned on to a temperature of 130 C. Sounds hot, but in such a small spot, and for such a short time, a person cannot even detect the heat, or feel any pain, as it is applied to the outer layers of skin.

This hotplate causes a tiny micro-pore to form through which a little bubble of fluid passively emerges. The bio-sensor then reads the glucose levels in the sample fluid through tiny electrodes coated with a substance that reacts specifically to the glucose.

The bio-sensor project initially began through funding from the military, with the intention of developing a miniature device to remotely monitor the health status of soldiers in a battlefield. This tiny prototype chip, which acts as a patch on the skin and is called the B-FIT (Bio-Flips Integrable Transdermal MicroSystem), can obtain samples of fluid from under the skin one time every hour for a 24-hour period.

To support the design and development of the device, Currie and Paranjape received a Department of Defense contract for $3 million over 3 years from DARPA (Defense Advanced Research Projects Agency).

In this application, troops being sent onto a battlefield could be fitted with biosensors. A medic in a central location could monitor significant changes in biomolecular levels, using a PDA or similar device, assessing for injuries or exposure to biological or chemical warfare agents. If the medic detected dangerous changes in a soldier’s body chemistry, the soldier could be removed from the field for medical care.

In the miniaturized world of micro- and nano-technology, novel measuring devices are possible, with multiple applications for health monitoring. Combining technical capabilities available through places like GAEL with biomedical research knowledge and a keen imagination opens many new doors. Dr. Paranjape and his colleagues in the Physics department are at the forefront of these new discoveries.

Print Article