  Traceability, security and freshness monitoring are crucial to the food and
pharmaceutical industries. Currently, barcodes and sensors are almost
exclusively located on product packaging. Making them edible and introducing
them into edible products could significantly enhance their functions. Here,
several types of microlasers made entirely out of edible substances were
developed. It is striking that olive oil already contains enough chlorophyll to
be used as a laser when dispersed in water as droplets. The edible lasers can
be embedded directly into edible products and serve as barcodes and sensors.
Due to their much narrower spectral lines compared to fluorescent or
color-changing sensors, they are significantly more sensitive to various
environmental factors. The edible lasers were employed to sense sugar
concentration, pH, the presence of bacteria, and exposure to too-high
temperatures. They can also encode tens of data bits, such as manufacturer's
information and expiration date. The microlasers are entirely safe for
consumption, do not change the appearance and taste of food considerably, and
are environmentally friendly. The developed barcodes and sensors could also be
applied to non-edible items, such as cosmetic and agricultural products, for
environmental monitoring and biomedical applications.
