Stale Food Stickers


Written by Kinsey Sullivan
05 Monday 05th March 2012



Composed of gold antennae, less than a micron thick, upon a pure silk protein substrate, the sticker is thin, minimalist, and flexible. It doesn't use a chip, but instead is an RFID-like sensor. Made of just silk and thin gold leaf, as thin as the kind used for dessert decorating, the sticker is completely edible. Silk, being a protein, is also fully digestible. 



The antennae in the sticker monitor the electromagnetic fluctuations resulting from the chemical changes that occur in food as it decays. These changes, known as dielectric changes, can be detected by the antennae as shifts in impedance and resonant frequency. As food decays, the electromagnetic frequencies it emits increase. Dielectric changes are evidenced in changes of dielectric properties like firmness, density, moisture, gas emission (like ethylene in fruit), salt content and composition; these dielectric changes can be interpreted as food freshness. Something as common as a smartphone could be used to read the stic


Other methods of quality control in industrial food productions required the destruction of a sample. Noninvasive food monitors used before this sticker were typically firm and were difficult to use on uneven foods.  But this sticker, flexible and adhesive, can work on eggs, apples, bananas, milk, any type of perishable. It's especially impressive that it can work on both foods and liquids, brittle and soft foods without peeling or cracking. It can even stick effectively on meat. In order to work in milk, the sensor just needs to be immersed and subsequently read. 



Made of silk, one of the strongest natural materials, the sticker can last for several months and is tear-resistant. Handling doesn't affect the accuracy of the readings either, which is critical to the sticker's usability, both for individuals and for companies. The silk substrate acts as the adhesive when introduced to water vapor. The diagram below explains how the sticker works:


As the silk substrate is exposed to water vapour, it softens but doesn’t fall apart. The silk melts minutely, allowing it to become more pliable. It then sculpts to the surface texture of the food it’s being applied to. An adhesive, thin layer of silk forms on the back of the substrate and acts as a glue to adhere the antennae to the food. The sensor can then be read.

Dr. Tao and the other scientists anticipate that these sensors will be used to ensure food safety, important for both quality control in the agriculture industry and for public health. Feasibly, they could be used by individuals, but there’s no information yet about price or whether these stickers are reusable.


Spoilt milk and squishy tomatoes really get to you? Share your thoughts, concerns, comments and questions below.

Don't Panic attempt to credit photographers and content owners wherever possible, however due to the sheer size and nature of the internet this is sometimes impractical or impossible. If you see any images on our site which you believe belong to yourself or another and we have incorrectly used it please let us know at and we will respond asap.