Breath test: Ouch-free sensors

U. FLORIDA—A tiny sensor that analyzes breath and saliva may provide inexpensive—and painless—diagnosis and monitoring for a variety of diseases, including diabetes, asthma, and breast cancer.

Early results by engineers at the University of Florida who designed and tested versions of the sensor are promising, particularly considering that the sensor can be mass produced inexpensively with technology already widely used for making chips in cell phones and other devices.

“This uses known manufacturing technology that is already out there,” says Fan Ren, professor of chemical engineering and one of a team of engineers collaborating on the project.

The sensor uses a semiconductor which amplifies minute signals to readable levels, contradicting long-held assumptions that glucose levels in the breath are too small.

“Instead of poking your finger to get the blood, you can just breathe into it and measure the glucose in the breath condensate,” Ren says.

The study was published in the January edition of IEEE Sensors Journal.

In the current study and other published work, the researchers report using the sensor to detect pH or alkalinity levels in the breath, a technique that could help people who suffer from asthma better identify and treat asthma attacks and calibrate the sensitivity of the glucose sensor.

The engineers have used other versions to experiment with picking up indicators of breast cancer in saliva, and pathogens in water and other substances.

Many testing methods currently in use are often cumbersome, expensive, or time-consuming, Ren says. For example, the current technique for measuring pH in a patient’s breath requires the patient to blow into a tube for 20 minutes to collect enough condensate for a measurement.

At 100 microns, or 100 millionths of a meter, the UF sensor is so small that the moisture from one breath is enough to get a pH or glucose concentration reading in under five seconds, Ren explains.

The sensors work by mating different reactive substances with the semiconductor gallium nitride commonly used in amplifiers in cell phones, power grid transmission equipment, and other applications.

If targeting cancer, the substance is an antibody that is sensitive to certain proteins identified as indicative of cancer. If the target is glucose, the reactive molecules are composed of zinc oxide nanorods that bind with glucose enzymes.

Once the reaction happens, “the charge on the semiconductor devices changes, and we can detect that change,” Ren explains.

While the sensor is not as acutely sensitive as those that rely on nanotechnology, the manufacturing techniques are already widely available, Ren says.

The cost is as little as 20 cents per chip, but the price rises considerably when combined with applications to transmit the information wirelessly to computers or cell phones.

The entire wireless-chip package might cost around $40, he says, although that cost could be cut in half with mass production.

“This is an important development in the field of biomedical sensors and a real breakthrough,” says Michael Shur, professor of solid state electronics at Rensselaer Polytechnic Institute.

“Professors Fan Ren and Steve Pearton have made pioneering contributions to materials and device studies of nitrides, and now their work has led to the development of sensors that might improve quality of life for millions of patients.”

The work was funded by NASA, the Office of Naval Research, the National Science Foundation, and the State of Florida.

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