MIT researchers have developed a new type of tiny, smartphone-readable particle that could tell if a food product is counterfeit.The particles, which are invisible to the naked eye, contain coloured stripes of nanocrystals that glow when lit up with near-infrared light.
Easily manufactured and integrated into a variety of materials, the particles can withstand extreme temperatures, sun exposure and heavy wear, according to Professor Patrick Doyle, a chemical engineer who is the senior author of a paper describing the particles in the journal Nature Materials.
The particles could also be equipped with sensors that can ‘record’ their environments, ensuring that they have been stored at the correct temperature to ensure the product doesn’t deteriorate.
The particles are about 200 microns long and include several stripes of different-coloured nanocrystals, known as rare earth upconverting nanocrystals, which contain elements such as ytterbium, gadolinium, erbium and thulium that emit colours when exposed to near-infrared light. By altering the ratios of these elements, the researchers can tune the crystals to emit any colour in the visible spectrum.
With the particles, the researchers can generate vast quantities of unique tags. With particles that contain six stripes, one million colour combinations are possible; this capacity can be exponentially increased by tagging products with more than one particle. For example, if the researchers created a set of 1000 unique particles and then tagged products with any 10 of those particles, there would be 1030 possible combinations - far more than enough to tag every grain of sand on earth.
The microparticles could be dispersed within electronic parts or drug packaging during the manufacturing process, incorporated directly into 3D-printed objects or printed onto currency, the researchers say.
“The ability to tailor the tag’s material properties without impacting the coding strategy is really powerful,” said MIT graduate student Paul Bisso. “What separates our system from other anti-counterfeiting technologies is this ability to rapidly and inexpensively tailor material properties to meet the needs of very different and challenging requirements, without impacting smartphone readout or requiring a complete redesign of the system.”
Another advantage to these particles is that they can be read without an expensive decoder like those required by most other anti-counterfeiting technologies. Using a smartphone camera equipped with a lens offering twentyfold magnification, anyone could image the particles after shining near-infrared light on them with a laser pointer. The researchers are also working on a smartphone app that would further process the images and reveal the exact composition of the particles.