Researchers at the University of Michigan have developed self-erasing chips that rely on a new material that temporarily stores energy, changing the colour of the light it emits. It self-erases in a matter of days, or it can be erased on demand with a flash of blue light.
"It's very hard to detect whether a device has been tampered with. It may operate normally, but it may be doing more than it should, sending information to a third party," said Parag Deotare, assistant professor of electrical engineering and computer science.
With a self-erasing bar code printed on the chip inside the device, the owner would know if it had been opened. Or a bar code could be written and placed on ICs or circuit boards, for instance, to prove that they hadn't been opened or replaced on their journeys. Likewise, if the lifespan of the bar codes was extended, they could be written into devices as hardware analogues of software authorization keys.
The self-erasing chips are built from a three-atom-thick layer of semiconductor laid atop a thin film of molecules based on azobenzenes — a kind of molecule that shrinks in reaction to UV light. Those molecules tug on the semiconductor in turn, causing it to emit slightly longer wavelengths of light.
Che-Hsuan Cheng, a doctoral student in material science and engineering in Deotare's group and the first author on the study in Advanced Optical Materials, is most interested in its application as self-erasing invisible ink for sending secret messages. To read the message, you have to be looking at it with the right kind of light.