Reinventing the Breathalyzer

Drunk driving crashes kills more than 10,000 people in the US each year.

On tool used to detect drunk drivers is the Breathalyzer which measures the alcohol content in a breath sample, it can detect when someone has had a drink, but not if they’ve had other drugs. And they require the driver’s consent to work, as opposed to being automatic.

The 13-year-old Krishna Reddy is one of 10 finalists in the Discovery Education 3M Young Scientist Challenge invented a device which can tell when a driver has consumed alcohol or used other drugs based on how dilated his or her pupils are.

Unhappy with the inability for breathalyzer to detect other substances, Krishna created a pupillary reflex computer program and apparatus that measures pupil dilation.

Our pupils constrict to filter the amount of light that gets into our eyes. When we look into a bright light, our pupils get smaller and when it becomes dark, our pupils dilate, or get bigger. This is known as the pupillary reflex.  While certain drugs, like alcohol and opioids, can cause our pupils to constrict, others can cause them to dilate.

Taking advantage of this effect, Reddy built a device made of three things: A digital camera, a snakehead flashlight, and a toilet paper roll.

The flashlight is held up to the eye, and the toilet roll directs the light onto the pupil. Then, the digital camera takes video of the pupil as it contracts. Measuring the ratio of pupillary reflex using special software lets you detect when a driver’s reflexes are impaired, and ultimately cut down on lethal traffic crashes.

Because the papillary reflex happens on the scale of millimeters and milliseconds, the device is far better than the naked eye at detecting a drunk or impaired driver.