Tiny particles could help verify goods

In this case, each polymer stream contains nanocrystals that emit different colors, allowing the researchers to form striped particles. So far, the researchers have created nanocrystals in nine different colors, but it should be possible to create many more, Doyle says.

Using this procedure, the researchers can generate vast quantities of unique tags. With particles that contain six stripes, there are one million different possible color combinations; this capacity can be exponentially enhanced by tagging products with more than one particle.

For example, if the researchers created a set of 1,000 unique particles and then tagged products with any ten of those particles, there would be 1,0³⁰ possible combinations — far more than enough to tag every grain of sand on Earth.

“It’s really a massive encoding capacity,” says Bisso, who started this project while on the technical staff at Lincoln Lab. “You can apply different combinations of ten particles to products from now until long past our time and you’ll never get the same combination.”

“The use of these upconverting nanocrystals is quite clever and highly enabling,” says Jennifer Lewis, a professor of biologically inspired engineering at Harvard University who was not involved in the research. “There are several striking features of this work, namely the exponentially scaling encoding capacities and the ultralow decoding false-alarm rate.”

Versatile particles
The microparticles could be dispersed within electronic parts or drug packaging during the manufacturing process, incorporated directly into 3-D-printed objects, or printed onto currency, the researchers say. They could also be incorporated into ink that artists could use to authenticate their artwork.

The researchers demonstrated the versatility of their approach by using two polymers with radically different material properties — one hydrophobic and one hydrophilic — to make their particles. The color readouts were the same with each, suggesting that the process could easily be adapted to many types of products that companies might want to tag with these particles, Bisso says.

“The ability to tailor the tag’s material properties without impacting the coding strategy is really powerful,” he says. “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.

The research was funded by the U.S. Air Force, the Office of the Assistant Secretary of Defense for Research and Engineering, the Singapore-MIT Alliance, the National Science Foundation, the U.S. Army Research Office, and the National Institutes of Health.

— Read more in Jiseok Lee et al., “Universal process-inert encoding architecture for polymer microparticles,” Nature Materials (13 April 2014) (doi:10.1038/nmat3938)

Reprinted with permission of MIT News