Smartphone-Screen-Integrated Optical Breathalyzer

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Researchers found a way to integrate breathalyzer into smartphones for detecting alcohol abuse anywhere and at anytime.

Breathalyzers for detecting alcohol abuse are critical for the safety of the public. Currently used breathalyzers are not at all compact, and people can’t carry them. The tragic accidents due to alcohol abuse can be greatly reduced if the public had access to a breathalyzer at any time and anywhere.

Researchers from the Centre for Optics, Photonics and Lasers (COPL) at Laval University, Canada, have analyzed how to embed a breathalyzer into smartphones. However, the idea of creating portable breathalyzer isn’t new, but the problem is that current technologies for detecting blood alcohol levels are not adequate to be integrated into phones. According to the researchers, they are bulky, expensive, complex to mass produce and not durable due to the need for chemical sensor replacements.

Researchers explored if existing components in phones could be used to measure blood alcohol content. This led to an optical breathalyzer integrated to the phone’s screen. The operating principle is fairly simple. It is based on the evaporation of the breath fog on the screen. When a screen is fogged, thousands of microdroplets form on the screen. When breath contains alcohol, these microdroplets evaporate faster.

To measure this evaporation rate, researchers used the phone display as a source of light. This light normally passes through the glass screen without being deflected to reach our eyes. However, when the screen is fogged, some of the light is coupled to the planar waveguide on the surface of the screen and guided to the side of the screen where a photodiode is placed to measure the light intensity. The coupling is due to the total internal reflection that occurs at the edge of each microdroplet.

The light intensity measured on the photodiode is proportional to the amount of microdroplets on the surface. If the intensity of light decreases faster, the breath contains alcohol. 

“We are very excited about this new technology that could make a real impact in society,” says Dr. Jerome Lapointe, first author of the article published in Sensors. “While the technology works well in a controlled environment, the ambient conditions in a real-world environment greatly affect the measurements. For example, if it is warmer or less humid, the fog on the screen evaporates at a faster rate. Therefore, it will be necessary to test in all possible conditions so that the breathalyzer can be calibrated. Fortunately, today’s phones have several sensors, including temperature and humidity ones, that can be used to record all conditions for each test. After accumulating a large database, we hope to use artificial intelligence by training a neural network to obtain accuracy that will convince major phone manufacturers to integrate the breathalyzer into screens.”

The research has been published in the journal Sensors.


 

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