Researchers at Purdue have developed an optical attachment and
smartphone app that allows users to objectively analyze and save results
from paper-based saliva alcohol tests
WASHINGTON–(BUSINESS WIRE)–A researcher team from Purdue
University, Indiana have developed a smartphone device and an app
that together quantitatively analyzes and store the results of
strip-based saliva alcohol tests — which is helpful, since the current
method consists of matching up the strip against a color scale on its
packaging. The dipsticks used are sensitive to the saliva alcohol range
of 0.02% to 0.30%, which is sufficient to determine if someone should be
operating a motor vehicle. Additionally, the app allows for storage and
recall of this data.
“It depends on your subjective interpretation of colors,” said Euiwon
Bae, senior research scientist, Purdue University School of Mechanical
Engineering, Indiana, “we try to avoid that, so we made a system that
can be easily integrated in a smartphone.”
Bae’s previous work has involved using lasers and optical methods to
provide quantitative measurements of samples, such as bacterial
colonies. He and his colleagues, working in collaboration with Novilytic
for alcohol sample preparation— a local startup company in West
Lafayette, Indiana — describe their device this week in Applied
Optics, a journal of The Optical Society.
The attachment itself is small, measuring 25 x 12 x 12 millimeters, and
consists of a plano-complex lens, mirror reflector, and plastic diffuser
that allow for consistent illumination conditions via the phone’s LED.
The strips fit into a small chamber above the camera lens, and the
device attaches to a metal strip in the smartphone’s case by way of a
weak magnetic strip. Because the device is manufactured in a laboratory
setting, the device’s plastic casing and lens are relatively low in cost.
The dipstick tests work by using a reaction between ethyl alcohol and
alcohol oxidase to produce hydrogen peroxide, which then mixes with the
enzyme ABTS and is converted by peroxidase, another enzyme, into a
green-colored complex. Darker hues correspond to higher ethanol contents.
This change is colorimetrically analyzed by an in-house MATLAB program
within the app that imports the images, crops them to a 120 x 120 pixel
center area and examines them with Red-Green-Blue and
Hue-Saturation-Value color schemes.
“With the app, you can record the digital image of your dipstick,
calculate the concentration, date and time of the recording, and also
geographical locations — everything is stored in the database of your
phone,” said Bae. “Practically speaking, if you are in the middle of a
legal dispute, you have proof at your fingertips — when it was taken,
where it was taken, what your concentration was, everything.”
Future work for Bae and his colleagues involves expanding the device’s
analytic applications in food safety. “When you have outbreak
situations, or even before you have them, one quick way to see whether
you have salmonella present is by using these assays,” Bae said.
Paper: Y. Jung, J. Kim, O. Awofeso, H. Kim, F. Regnier, E. Bae. “Smartphone-based
colorimetric analysis for detection of saliva alcohol concentration,”
Applied Optics 54, 9189-9189 (2015).
About Applied Optics
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