A strong full-spectrum white light spectrometer captures the reflected light pattern from the silica particles, which can be added to nutritional supplements' coating or inside the supplement itself. The reflected spectral pattern is then matched to the silica microtag's pattern to confirm that the supplement contains the tag.

Depending on the size of the pill, there could be many hundreds or thousands of the particles, which are 75-100 microns small, or about the width of a human hair. "We don't have to look for a needle in a haystack," said Wong. The spectrometer can be programmed to read a certain amount of tags to achieve mathematical certainty for verifying products.

"We've tested it with a prominent nutritional supplement maker, where you sprinkle a small vial of these silica particles in a big vat of tablet coating mix," said Wong. "Think of it as a small pinch of sugar to the frosting mix." As the pill cores are tumbled, the tablet coating's fine mist sprays the microtags onto the pills along with the coating. "Some of them get buried in the first 10-15 minutes of the coating process and some of them land on the surface. We read the ones on the surface."

For capsule products, putting the silica in shell gelatin or the banding solution are options. Or the tags could be placed inside the pill's ingredient mix—if the shells are clear so they can be scanned.

"You could use a lot less silica by mixing it into the pill core, and then it's a forensic use," said Wong, noting that if there's an incident in the field, the pill can be recalled, ground down and identified to discover at which facility it was manufactured and when, and even the exact lot it came from. "We can make up a trillion different spectral patterns," said Wong, likening the pattern to a traditional bar code.