For the 21 million Americans with diabetes, a finger prick is a part of daily life. To check their body’s level of sugar, or glucose, they have to place a drop of blood on the end of a chemically coated strip, and then place the strip in a handheld machine. And doctors say diabetics should check their glucose level often during the day—before eating, taking insulin, doing physical activity, or going to bed.
“But there are a lot of people who just don’t want to do this,” says the Whiting School’s Jin Kang, professor of electrical and computer engineering. “It’s especially bad for young kids.”
Hundreds of engineering teams across the country are trying to come up with a way to test glucose levels without the painful prick. Now, Kang has designed a prototype that’s not only noninvasive, but compact, inexpensive, and precise. He imagines a machine that costs a few thousand dollars and could be set up in schools, daycare centers, and nursing homes— “something like the blood pressure stations they have in shopping malls,” he says.
Kang’s device begins with two lasers, one a continuous wave used as a signal laser, and the other a tunable pump laser. The lasers hit, say, the finger, penetrate the skin, and scan the pumping blood stream within. Because of the intrinsic molecular properties of the skin, not all lasers can do this. Skin proteins absorb UV light, for instance, so a UV laser wouldn’t penetrate to the blood. Kang’s laser uses the relatively longer wavelength of near-infrared light.
After photons of light hit an object, most of them have the same energy, and wavelength, as before the collision. But a tiny fraction of photons is scattered at different energy levels, depending on the vibrational energy levels of whatever atom or molecule has been hit. This is called Raman scattering, and Kang’s device takes advantage of it.
The blood molecules within that exposed finger, he explains, would scatter light with wavelengths that are shifted. When the wavelength difference between the two lasers matches the shifted wavelength, changes occur in the signal laser. Then an optical device would detect the changes in the signal, and subsequent signal processing would measure the precise concentration of glucose molecules in the blood.
One of the advantages of Kang’s table-top prototype is that all the parts are fiber optic, meaning that all of the light is transmitted within tiny, transparent, and—most importantly— durable tubes. “Traditional lasers and optics,” Kang says, “have mirrors everywhere, and lenses, and light comes out through the free space. If you move one of the components it won’t work anymore.” In contrast, fiber optic systems stay safe and sound within enclosed pipelines. Kang has made and tested all of the various parts of his system in the lab. Next is putting them together into a workable shoebox-sized prototype that can be tested in clinical studies.
Kang is well aware of the device’s potential market. Working through the intellectual property office at the Homewood Schools, he has filed a patent application. Says Kang, “I noticed a sign on campus for a meeting about venture capitalism. I’ll go and see what it’s all about.”