With ever-increasing consumer demand, the food and pharmaceutical industries are in dire need of innovative platforms to track the quality and freshness of their products to ensure safety as well as to minimize waste. Intelligent sensors integrated in the packages of food or pharmaceutical products can report the levels of crucial parameters like pH or humidity and can therefore be used to monitor the quality of packaged food or pharmaceutical items. These intelligent sensors can overcome the complicated handling steps and associated expenses often encountered with conventional techniques such as mass spectrometry, DNA barcoding, isotope and elemental fingerprints, and gas chromatography.
But smart sensors or barcodes incorporated on packaging materials can be easily manipulated or removed and are not useful for monitoring unpackaged items. A solution to these situations is the incorporation of barcodes and/or sensors directly on the edible products, without altering the product’s taste or appearance, enabling the remote readout of various parameters using hand-held scanners.
Microlasers can be a game changer in this context.
Microlasers are miniaturized lasers consisting of three main components, namely, a gain medium, a pumping source, and an optical microcavity. Gain medium amplifies light through stimulated emission. The pumping source provides the energy to the gain medium to create population inversion required for laser action. Laser cavity is a confined space consisting of reflectors with a gain medium enclosed between them, which allows the light to undergo multiple reflections leading to light amplification. Microlasers are gaining popularity for use in biomedical applications, sensors, and barcoding… and it is now possible to directly integrate them on food products.
Matjaž Humar and co-workers at the J. Stefan Institute and the University of Ljubljana (Slovenia) as well as the Aristotle University of Thessaloniki (Greece) report the fabrication of environmentally friendly, all-edible microlasers, where all components are made from edible substances. The researchers systemetically investigated various edible dyes such as Chlorophyll-A, Riboflavin (Vitamin B2), and Bixin as gain media, edible oil, butter, agar, gelatin, and chitosan as cavity materials, and thin silver/aluminium leaves used for decorating sweets as reflectors. Different cavity geometries were explored to produce microcavities suitable for food applications.
“During the development of edible lasers,” says Dr. Humar, “to our amazement, we discovered that olive oil droplets in water are already natural lasers. They only need to be excited by an external source of light. The olive oil is green due to chlorophyll, which is an excellent laser gain material… while the smooth spherical shape of the droplet acts as a laser cavity.”
The group demonstrated that the peak position of the lasing spectrum generated from chlorophyll-doped sunflower oil droplet microcavities depends on the droplet size and refractive index of the surrounding medium. For information encoding, selected droplet sizes are added into the sample. Droplet sizes can be calculated from the spectrum generated when the food product is scanned with a laser. Using 14 different sets of monodispersed droplets with non-overlapping sizes, a total of 214 =16,384 unique combinations of binary digits can be generated based on whether each size is present in the sample (1) or not (0). This can be used to encode binary information such as the date of manufacture or expiry, country of origin, and much more, directly inside the food product.
Furthermore, the emission from microcavities can be exploited to determine properties such as the sugar concentration of alcoholic beverages, honey, or maple syrup, which have different refractive index. Edible microlaser sensors can also detect changes in the pH of the surrounding medium and the growth of microorganisms in the food and pharmaceutical products, as well as provide a read-out of the temperature.
The emission from microcavities can be read remotely through sealed and transparent packaging, allowing a rapid online product monitoring without any need for sample collection. Though the researchers used a pulsed laser and a high-resolution spectrometer for their studies, they envision that a continuous-wave laser or an LED source for excitation could be used for practical uses, and the read-out could be done using a pocket-sized spectrometer.
Future studies will investigate additional parameters related to food safety and freshness by exploring other natural ingredients or by developing responsive edible materials. The applications can be extended to cosmetics, agricultural products, environmental monitoring and biomedicine.
Reference: A R Anwar et al., Microlasers Made Entirely from Edible Substances, Advanced Optical Materials (2025). DOI: 10.1002/adom.202500497
Featured Image: David Clode via Unsplash
