Memory and Storage

“Spray-on” Memory Opens the Door for Future Bendable Storage Devices

04 April 2017

Ubiquitous USB flash drives are used by many to transport information from one device to another or for storing information that is easy to distribute.

Researchers at Duke University are working on a technology that could one day enable this type of technology to be expanded to nearly anything we interact with.

The technology is a new “spray-on” digital memory device that is applied using only an aerosol jet printer and nanoparticle inks that could significantly progress the move to flexible electronics. Duke claims the device is the first fully-printed digital memory that could be used in simple electronics such as environmental sensors and RFID tags.

Duke University’s “spray-on” memory (upper left) could be used to build programmable electronics on materials such as paper, plastic or fabric. Source: Duke UniversityDuke University’s “spray-on” memory (upper left) could be used to build programmable electronics on materials such as paper, plastic or fabric. Source: Duke University

Because the technology is jet-printed at low temperatures, it could be used to build programmable electronic devices on bendable materials such as paper, plastic or fabric. At the core of the device, which is about the size of a postage stamp, is copper-nanowire-based printable material capable of storing digital information.

How They Did It

Unlike traditional flash drives, the new material—made of silica-coated copper nanowires encased in a polymer matrix—encodes information not in states of charge but instead a state of resistance. Meaning, a small voltage can be applied and it switches between a state of high resistance, which stops electric current, and a state of low resistance, which allows current to flow.

Unlike silicon, the material can be dissolved in methanol, which creates a liquid that can be sprayed through the nozzle of a commercially available gold nanoparticle ink printer. To make the device, researchers printed a series of gold electrodes onto a glass slide and then printed the copper-nanowire memory material over the gold electrodes and then printed a second series of electrodes but this time in copper.

This would allow the memory to be sprayed to fabrics, RFID tags or curved and flexible substrates, researchers say.

While Duke researchers caution the memory is still in the beginning phases and it can’t store digital photos or music as the capacity is too small, it could be useful in applications where low cost and flexibility are key.

“For example, right now RFID tags just encode a particular produce number, and they are typically used for recording inventory,” says Benjamin Wiley, an associate professor of chemistry at Duke. “But increasingly people also want to record what environment that product felt—such as, was this medicine always kept at the right temperature? One way these could be used would be to make a smarter RFID tags that could sense their environments and record the state over time.”

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