These Tiny Lasers Are Completely Edible

'Scientists have created the first lasers made entirely from edible materials,' reports Science magazine 'which could someday help monitor and track the properties of foods and medications with sensors that can be harmlessly swallowed.'

[The researchers' report] shows that tiny droplets of everyday cooking oils can act like echo chambers of light, otherwise known as lasers. By providing the right amount of energy to an atom, the atom's electrons will excite to a higher energy level and then relax, releasing a photon of light in the process. Trap a cloud of atoms in a house of mirrors and blast them with the right amount of energy, and the light emitted by one excited atom will stimulate one of its neighbors, amplifying the atoms' collective glow...
[The researchers] shot purple light at droplets of olive oil, whose surfaces can keep photons of light bouncing around, trapping them in the process. This reflected light excited the electrons in the oil's chlorophyll molecules, causing them to emit photons that triggered the glow of other chlorophyll molecules — transforming the droplet into a laser. The energy of the chlorophyll's radiation depends on the oil droplets' size, density, and other properties. The study's authors suggest this sensitivity can be exploited to track different properties of food or pharmaceutical products.
When researchers added oil droplets to foods and then measured changes in the laser light the droplets emitted, they could reliably infer the foods' sugar concentration, acidity, exposure to high temperatures, and growth of microorganisms. They also used the lasers to encode information, with droplets of different diameters functioning like the lines of a barcode. By mixing in sunflower oil droplets of seven specific sizes — all less than 100 microns wide — the researchers encoded a date directly into peach compote: 26 April, 2017, the first international Stop Food Waste Day.
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