Invisible ink isn’t a new idea, in fact “smart inks” are commonly utilized for storing sensitive information.
However, these inks are typically activated light or heat, enabling the user to then access or read the data/information.
However, there is one major drawback which is hard to ignore at the moment.
For starters, the base compound of the invisible ink is lead, which of course, can prove to be toxic in large doses.
After applying a special type of salt, the lead transforms into nanocrystals that glow when exposes to a UV lamp. Upon reapplying the salt, the ink becomes invisible once again, which is great for security purposes.
The scientists are working to make the new development safer, so we’ll have to wait for what appears to be a futuristic version of passing notes.