A team from the University of Michigan have developed self-erasing chips that can prevent counterfeiting in electronics or send alerts in the event of tampering with cargo and shipment.

The new security technology relies on a new material that can store energy temporarily, responding by shifting the color of the light it emits. This material erases itself after a few days, or when flashed with blue light.

The results of the study are published in the journal Advanced Optical Materials, September 24.

A Novel Tampering Countermeasure

"It's very hard to detect whether a device has been tampered with," explained Parag Deotare, and author of the study and an assistant professor in electrical engineering and computer science at the University of Michigan. "It may operate normally, but it may be doing more than it should, sending information to a third party."

If a self-erasing bar code is attached to a chip in an electronic device, like a smartphone or Smart TV, the owner gets a way of learning whether it had been opened or tampered with, as is the case should someone try to install a tracker or a bug to listen. A similar device would prove useful in ensuring that integrated circuits or microchips had not been opened during transport.

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The work, which utilizes nanoscale strain engineering, are created from carefully laying a semiconductor approximately three atoms thick on top of a molecular film based on a chemical compound that contracts upon exposure to UV light, known as azobenzenes. The shrinking of the azobenzenes also pulls the semiconductor material above it, causing the change in the color of the light emitted.

With this hybrid combination of materials, the self-erasing strain can be relaxed under exposure to visible light. Conversely, it can stay for up to seven days in a dark environment.

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Reading the Self-Erasing Codes

First author and doctoral student Che-Hsuan Cheng explained, in a University press release,  that to read the embedded message, you need the "right kind of light." He also expressed interest in its potential as a self-erasing "invisible ink" for communicating secret messages.

Researchers also described it as a "beyond graphene" material that shares several similarities with the revolutionary graphene, surpassing it in one feature: emitting light in selected frequencies.

The team included Material Science and Engineering professor Jinsang Kim and doctoral student Da Seul Yang, who designed and made the molecules. Cheng then floated a single layer of the molecules on a water bath, before dipping a silicon wafer to allow the molecules to coat it.

Next, the chip was layered with the semiconductor material in Deotare's laboratory. Using what they termed as the "Scotch tape" method, Cheng applied an adhesive of some sort, tungsten diselenide, on the surface of the semiconductor and used it to draw single layers of the material.

It resulted in a layer of tungsten sandwiched in between two layers of selenium atoms. They later stamped the sandwiched semiconductor on top of the azobenzene chip.

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Now, the researchers are looking to better observe the length of time that this self-erasing chip can maintain its message intact, further exemplifying its use as an anti-counterfeiting measure.

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