The internal camera of a smartphone can function as a high-resolution laboratory spectrometer to provide measurements that match the sensitivity performance of large and expensive laboratory instruments for popular analytic tests used in medical diagnostics, food safety and other applications.
Results of the research by scientists at the University of Illinois at Urbana-Champaign were published in the November 2014 issue of Biomedical Optics Express. The UI team, led by Brian T. Cunningham, professor in the Department of Bioengineering and Electrical and Computer Engineering, also includes Kenneth D. Long, graduate student in Bioengineering, and Hojeong Yu, graduate student Electrical and Computer Engineering.
“In our research, we focused on conducting common biological tests — assays — for two different proteins, one that measures inflammation, such as what might occur due to cancer, diabetes or other diseases, and another used to detect the peanut allergen,” Cunningham said. These assays detect the presence of substances such as proteins by passing light through a liquid sample. The concentration of the substance is determined by the color of the liquid.
What Cunningham and his team did differently from previous researchers was to use the phone’s camera to spread the light’s wavelengths over the camera’s pixels. That change was made possible by a cradle the team constructed that contains a series of lenses and optical filters. The cradle holds the phone’s camera in alignment with the optical components.
“For the research described in the paper, we used an incandescent bulb as our light source,” Cunningham said. “The light passes through the liquid test sample, then goes through a second lens that focuses the light down to a diffraction grating, placed right in front of the phone’s back-facing camera. The diffraction grating spreads out the light’s wavelengths over the camera’s pixels, capturing a picture of the spectrum.”
By generating the entire optical spectrum instead of the single wavelength that a traditional laboratory detection instrument would measure, Cunningham and his team also received a greater degree of test information than is typically available.
“This system is geared toward point-of-use applications with a low number of tests to perform, such as in a home care setting, rather than a hospital or lab,” Cunningham said. “There are also numerous business applications for manufacturing quality control or quality monitoring of food ingredients.”
Cunningham’s group is working now to make the unit self-contained by incorporating all components into the cradle. In the new version, an optical fiber placed in front of the camera’s flash unit replaces the external incandescent bulb.
The research builds on Cunningham’s previous work with the cradle and iPhone. He recently received a National Science Foundation grant to continue developing the “lab-in-a-smartphone” concept.
The group’s paper is available online at Biomedical Optics Express.
Editor's note: Read more about Prof. Cunningham and team's work with smartphones and biosensors.