The approach, developed by researchers in China,
Forget lemon juice and hot irons, is a new way to write and read invisible messages paper coated with manganese-containing chemicals.
Invisible ink graphic.
Invisible ink graphic.
Invisible ink graphic
"Data leakage has become a global problem with terrible consequences, including outbreaks of war and severe economic and human life"
Writing in English in the journal Matter, the team say other approaches to "secure printing" include the use of fluorescent inks that can only be seen under UV light. However, they say they have drawbacks, including that they can not be erased, and are predictable ̵
The team report that they have developed a number of solutions to tackle each of these problems. The new approach involves coating paper with a polymer that has manganese-containing chemicals, which can absorb UV light and emit green light, and then printing it on paper with pure water using an inkjet printer. The team said they have very low toxicity.
When the pure water interacts with the manganese-containing chemicals, it disrupts their structure, hence their photoluminescent properties. The upshot is that while the message can not be seen with the naked eye, it shows up as a dark under UV light.
If the paper is heated for about 30 seconds, the message disappears.
"If we can find a good substrate to replace filter paper, we believe the cycle numbers Will be improved, "said Dr Yun Ma, co-author of the study, from Nanjing University of Posts and Telecommunications.
The authors said the message did not just disappear with water in the absence of a hairdryer,
One possible explanation, they say, is that it may be necessary for the polymer coating to make the necessary movement for the structure (and hence photoluminescence) of the manganese -containing chemicals.
The team thus took a different approach, using two manganese-containing inks to print a message on a different type of coated filter paper.
The message can not be read by the naked eye or, importantly, under UV light since the similarity in the midst of light. However, the message may not be read using time-based imaging techniques.
Developing this further, the team has come up with an even more sophisticated approach
By tracking the intensity of light emission over time, a new order of numbers is revealed code to be cracked.
"This information decryption method has an extremely high security level and might be promising in military and economic domains, "the team said.