Researchers have developed inexpensive breathalyzers integrated into the screens of smartphones or wearables. The new technology uses the evaporation rate of the fog produced by the breath on the phone screen, which increases with increasing breath alcohol content.
The breathalyzers use a photodiode placed on the side of the screen to measure the signature of the scattered light intensity from the phone display guided through the stress layer of the Gorilla glass screen. The evanescent field induced at the edge of the breath microdroplets couples a part of the display light to the stress layer.
The intensity signature measured at the detector is proportional to blood alcohol content. The researchers fabricated a prototype in a smartphone case powered by the phone’s battery, controlled by an application installed on the smartphone, and tested it in real-world environments.