Researchers from Purdue University have developed a new type of sensor that allows rapid detection of chemical compounds in a person's respiration. The new approach is at least 100 times more accurate than current technologies - detecting biomarkers in the parts per billion to parts per million range - and may lead to wide-spread use of breathalyzers in detecting the possible presence of cancer and other diseases.

The technology works by detecting changes in electrical resistance or conductance as gases pass over sensors built on top of tiny heating devices on electronic chips, called "microphotplates".

Carlos Martinez, assistant professor of Materials Engineering, and key investigator of the new sensors commented; "We are talking about creating an inexpensive, rapid way of collecting diagnostic information about a patient. It might say, 'there is a certain percentage that you are metabolizing a specific compound indicative of this type of cancer,' and then additional, more complex tests could be conducted to confirm the diagnosis."

To demonstrate the principle, the researchers used the new technology to detect acetone (a biomarker for diabetes) with a sensitivity in the parts per billion range in a gas which mimicked a person's breath.

The researchers used a template made of micron-size polymer particles and coated them with far smaller metal oxide nanoparticles. Using nanoparticle-coated microparticles instead of a flat surface allows researchers to increase the porosity of the sensor films, increasing the "active sensing surface area" to improve sensitivity.

A droplet of the nanoparticle-coated polymer microparticles was deposited on each microhotplate, which are about 100 microns square and contain electrodes shaped like meshing fingers. The droplet dries and then the electrodes are heated up, burning off the polymer and leaving a porous metal-oxide film, creating a sensor.

"It's very porous and very sensitive," Martinez said. "We showed that this can work in real time, using a simulated breath into the device."

Gases passing over the device permeate the film and change its electrical properties depending on the particular biomarkers contained in the gas.

Such breathalyzers are likely a decade or longer away from being realized, in part because precise standards have not yet been developed to manufacture devices based on the approach, Martinez said.

"However, the fact that we were able to do this in real time is a big step in the right direction."

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