Researchers fabricate the world's smallest QR code using infrared information carrier

Credit cards embedded chips, national mints printed watermarks, and high-profile locations installed retina scanners all for the same reason—to protect information. As attackers grow smarter, so must defense.

Sheng Shen, professor of Mechanical Engineering, along with collaborators at Penn State University, have developed a pixel-by-pixel approach to visible camouflage with hopes of scaling it for enhanced infrared surveillance, optical security, and anti-forgery protections. The research is published in the journal Science Advances.

'Our collaborators came to us with brochosomes—a 'magic' structure leafhoppers produce to create a cloak effect to hide from predators,' Shen said. 'We wanted to understand brochosomes' optical limitations to see what more we could do with them.'

Brochosomes are 3D soccer ball-like objects with nanoscale cavities that internally absorb light rather than reflect it onto outside structures. In nature, biologists suspect that this allows leafhoppers to blend in with their background.

To test functionality, the team simulated two different versions of the structure, one with cavities for light absorption and one without.

There is a fundamental law in physics that if a structure is a good absorber of energy it can emit an equal amount of energy, explained Zhuo Li, Ph.D. candidate at Carnegie Mellon. 'We quickly realized that if we put both structures together one would emit more energy than the other. That would make one appear brighter to an infrared camera than the other.'