This Message Will Self Destruct: Scientists Develop Programmable, Self-Erasing Documents

Self-Erasing Documents Powered By Disappearing Nanoparticles

Remember when, as a kid, you would pass “top-secret” notes written in lemon juice that your friends could only read in the right light? Well, in light of new nanotechnology research, this now sounds absurdly antiquated, like cave painting in the modern era. Instead, the youth of the future (and adults, too) could have to option to communicate via documents that self-erase at a programmed time.

The idea comes from Northwestern University, where a team of researchers led by Bartosz Grzybowski is making use of a unique property of certain nanoparticles-–their ability change color based on how close they are to one another. So, when spread out, gold nanoparticles are red, but once you pack them together, they turn violet, blue, and then become colorless. To change the distribution of the particles, you can coat them with MUA molecules, which, when struck by ultraviolet light, will relocate.

In their lab, Grzybowski and his colleagues have taken to shining UV light on a thin film made up of a gel of nanoparticles placed between two plastic sheets. The result? They were able to display images and text that disappeared after a programmed period of time.

This now-you-see-it-now-you-don’t concept is not entirely new: back in 2006, Xerox came up with a type of paper whose print would fade after about 16-24 hours, making it possible to reuse photocopies. That design, however, came with neither a color option nor the possibility to control the timing of the text’s vanishing--both of which Grzybowski’s team can do.

Future uses of this research include anything from limited-time bus tickets to military documents that would wipe themselves clean. Imagine the possibilities! I bet the Bush administration wishes it could have gotten its hands on this.

[New Scientist]