James Bond, get ready to put your skills to the test.
The images depict printed patterns created by the lead-based invisible ink, shown under UV light. From left to right: Butterfly with intricate details, QR codes, text in English. Photo Credits: Congyang Zhang et al., 2017.
Scientists from People’s Republic of China created an invisible ink that easily switches on and off. These findings, published in the journal Nature as a research article titled Conversion of invisible metal-organic frameworks to luminescent perovskite nanocrystals for confidential information encryption and decryption, provide a glimpse into the future of high-security information encryption. Unfortunately, there’s one huge drawback: lead, the invisible ink’s main component, can be poisonous in large quantities.
Invisible ink uncovers counterfeit money and stores private information by keeping written content hidden from the naked eye. Ideally, invisible ink remains undetected until treated with UV light, however, previous invisible inks left residues resembling wet paper. The new lead-based invisible ink material leaves no residue, hiding secret information unsuspiciously.
Lead-based invisible ink is composed of a yellow powdered salt which turns clear in solution. The salt, composed of extremely tiny crystals known as nanocrystals, glow under UV light.
The powdered salt, shown in normal light (left) and UV light (right) This salt MABr is the foundation for the on/off switching properties of lead-based invisible ink. Photo Credits: Congyang Zhang et al., 2017.
The lead-based ink becomes invisible with the addition of methanol, a common antifreeze. UV light cannot detect the ink after the methanol treatment, making the invisible ink undetectable. The hidden lead-based ink, easily passed around without fear of UV detection, will safely enclose the confidential information. Reapplication of the custom-made salt triggers the ink’s UV-detectable properties, making the information visible again. This manual on/off switch adds an extra layer of protection against UV lights.
Reversibly switching of invisible ink: The researchers’ university logo is encrypted by methanol (MeOH) and then decrypted by adding salt (MABr). All three images are shown under UV light. Photo Credits: Congyang Zhang et al., 2017
The scientists found the ink did not fade over a testing period of three months; the ink lasted over 20 on/off switches. This means the lead-based ink can be useful for long-term important documents. Realistically, the toxic lead component must be replaced by safer alternatives before the ink can be used globally.
Although scientists plan to use the lead-based invisible ink mainly for increasing security of anti-counterfeit measures, the ink’s virtually undetectable qualities must be approached with skepticism. In the wrong hands, such as the hands of corrupt spies and drug lords, this lead-based invisible ink can destroy our society.
Will the potentially life-changing applications of this on-and-off invisible ink outweigh the risky consequences?
Only time will tell.
– Jessica Shi
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