Science

Laser "pinging" shows promise for fast and cheap water testing

Laser "pinging" shows promise ...
The current setup incorporates a laser tattoo removal machine that's hooked up to a fiber optic cable
The current setup incorporates a laser tattoo removal machine that's hooked up to a fiber optic cable
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By measuring the amount of time that passes between each laser flash occurring and the accompanying sound reaching the mic, it's possible to determine the speed at which the sound waves are travelling through the water
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By measuring the amount of time that passes between each laser flash occurring and the accompanying sound reaching the mic, it's possible to determine the speed at which the sound waves are travelling through the water
The current setup incorporates a laser tattoo removal machine that's hooked up to a fiber optic cable
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The current setup incorporates a laser tattoo removal machine that's hooked up to a fiber optic cable

Looking for impurities in drinking water or other liquids typically involves chemical analysis, which may be time-consuming. Now, however, scientists have created an inexpensive system in which light – that's converted to sound – is used to instantly determine if water is safe to drink.

Being developed by a team at the University of Missouri, the setup utilizes a commercially-available laser tattoo removal machine, which emits a series of 10-nanosecond-long laser-light flashes. These flashes travel down a fiber optic cable, the other end of which is submerged in a small water sample. That end of the cable is also covered in paint-on liquid electrical tape.

In what is known as the photoacoustic effect, the light rapidly heats the tape, causing it to vibrate and emit pulses of sound. The sound waves travel through the liquid, and are detected by a microphone.

By measuring the amount of time that passes between each laser flash occurring and the accompanying sound reaching the mic, it's possible to determine the speed at which the sound waves are travelling through the water
By measuring the amount of time that passes between each laser flash occurring and the accompanying sound reaching the mic, it's possible to determine the speed at which the sound waves are travelling through the water

By measuring the amount of time that passes between each laser flash occurring and the accompanying sound reaching the mic, it's possible to determine the speed at which the sound waves are travelling through the water. Should the sound not be moving as fast as it would be in untainted water, that means there's something else in the sample, slowing the sound waves down.

"If the water isn't drinkable, then our method will tell you that something is wrong with the water," says Assoc. Prof. Luis Polo-Parada. "For instance, if a facility removes salt from sea water in order for water to be safe for drinking, our method can help alert the facility to potential changes such as an issue with the desalination process."

It is hoped that once the technology is developed further, it could also be used to inspect other liquids – this could include checking for inferior oil diluted into supposedly high-quality olive oil, assessing the quality of liquid honey, or determining the amount of artificial sweeteners or sugar added to soft drinks.

A paper on the research was recently published in the journal Sensors and Actuators, B: Chemical.

Source: University of Missouri

2 comments
ljaques
Why does this feel like a simple turbidity tester to me rather than a water safety tester? A laser can't tell you anything about toxicity or the nature of the substance in the liquid at all. It can only tell you the percentage of blockage of light, and there are already numerous schemes available in the marketplace for this. Someone really stretched on this one, and this should never have made it to release.
Nobody
This sounds totally ridiculous and dangerous unless some sort of spectrum or chemical signature can be identified for each contaminate. This is necessarily complex since there are so many toxins, minerals and dissolved gases that could be in the water. The salinity example was completely ridiculous since a simple conductivity test would quickly show some sort of contamination. What sort of contamination would require more testing.