Researchers and physicians in the field could soon run on-the-spot tests for environmental toxins¹, medical diagnostics, food safety and more with their smartphones. University of Illinois at Urbana-Champaign researchers have developed a cradle and app for the iPhone that uses the phone's built-in camera and processing power as a biosensor to detect toxins, proteins, bacteria, viruses and other molecules².

 

Having such sensitive biosensing capabilities⁴ in the field could enable on-the-spot tracking of groundwater contamination, combine the phone's GPS data with biosensing data to map the spread of pathogens, or provide immediate⁵ and inexpensive medical diagnostic tests in field clinics or contaminant checks in the food processing and distribution chain.

 

"We're interested in biodetection that needs to be performed outside of the laboratory," said team leader Brian Cunningham, a professor of electrical and computer engineering and of bioengineering at the U. of I. "Smartphones are making a big impact on our society -- the way we get our information, the way we communicate. And they have really powerful computing⁶ capability⁷ and imaging. A lot of medical conditions might be monitored very inexpensively and non-invasively using mobile platforms like phones. They can detect molecular⁸ things, like pathogens, disease biomarkers or DNA⁹, things that are currently only done in big diagnostic labs with lots of expense and large volumes of blood."

 

The wedge-shaped cradle contains a series of optical components¹⁰ -- lenses and filters -- found in much larger and more expensive laboratory devices. The cradle holds the phone's camera in alignment¹¹ with the optical components.

 

At the heart of the biosensor is a photonic crystal. A photonic crystal is like a mirror that only reflects one wavelength¹² of light while the rest of the spectrum¹³ passes through. When anything biological attaches to the photonic crystal -- such as protein, cells, pathogens or DNA -- the reflected color will shift from a shorter wavelength to a longer wavelength.

 

For the handheld iPhone biosensor, a normal microscope slide is coated with the photonic material. The slide is primed to react to a specific target molecule³. The photonic crystal slide is inserted into a slot on the cradle and the spectrum measured. Its reflecting wavelength shows up as a black gap in the spectrum. After exposure to the test sample, the spectrum is re-measured. The degree of shift in the reflected wavelength tells the app how much of the target molecule is in the sample.

 

The entire test takes only a few minutes; the app walks the user through the process step by step. Although the cradle holds only about $200 of optical components, it performs as accurately¹⁴ as a large $50,000 spectrophotometer in the laboratory. So now, the device is not only portable, but also affordable¹⁵ for fieldwork in developing nations.

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