People with diabetes could soon be waving goodbye to the pain and hassle of needles, thanks to a new under-skin sensor that monitors blood sugar levels with a simple wave of the arm.
The sensor, which is smaller than a dime and paper thin, is based on the same theory behind plastic security tags used in stores to prevent shoplifting. The device, which will be described in the July 15 edition of Analytical Chemistry, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society, also shows promise for monitoring environmental toxins and terrorism agents like ricin.
"The vision of our work is a passive sensor of virtually unlimited lifetime that could be placed in the tissue of the skin," says Craig Grimes, Ph.D., a professor of electrical engineering at Penn State University and lead author of the paper.
Designed as an inexpensive device to continually monitor the blood glucose levels of people with diabetes, the passive sensor requires no internal power supply and no connections outside the body, according to Grimes and his associates. "Whenever a reading is needed, a person can wave their hand or arm in front of a reader that will automatically detect the sensor," Grimes says.
The sensor is based on "magnetoelastic" technology, just like the plastic security tags on store merchandise, which are sensed wirelessly as they pass through an exit.
"The cost of these anti-theft markers is a penny," Grimes says. "We've leveraged off that same premise, so the material cost associated with the sensors is effectively zero." The electronics used in the reader, which is about the size of a wristwatch, cost approximately $50, the researcher estimates.
"Magnetoelastic sensors can be considered the magnetic analog of an acoustic bell," Grimes explains. "If you hit a bell with a hammer, the bell rings at a characteristic frequency. If you coat the bell with a layer of paint, the frequency changes." Likewise, the molecules in a magnetoelastic sensor vibrate in the presence of a magnetic field, and the frequency varies with different chemical coatings.
Grimes' glucose sensor is coated with a polymer that responds to changes in acidity, and then coated with the chemical glucose oxidase. The glucose oxidase reacts with blood glucose to produce an acid, which causes the polymer to swell and changes the frequency of the sensor. The reader then interprets these changes as blood glucose levels.