Counterfeit goods producers are flooding the global market with low-quality, sometimes dangerous merchandise and ripping off brand-name manufacturers. A new technique developed by a team of researchers at the Korea Advanced Institute of Science and Technology (KAIST) can add an innovative authenticity tag to counter piracy.
Named after the two-faced Roman god Janus, the term "Janus Particles" often refer to tiny particles that possess two distinct physical properties. Its first appearance in scientific articles was used to describe glass beads with one of a hydrophilic side and a hydrophobic side.
The Korean team created their "Janus Balls" by tinkering with the optical nature of colloidal crystals. Their particles are made out of two photocurable resins by a microfluidic instrument. One of the resins contains magnetic nanoparticles and carbon black, and the other one has silica particles with a high volume fraction.
Under normal circumstances, the particles would appear as black. When placed in a magnetic environment, their "Janus balls" would align their magnetic moment to the field and exhibit their structural colors, which allow them to act as an anti-counterfeit label.
This research is recently reported in the journal ACS Nano.
Source: ACS via Youtube