Transparent “Spray On” Digital Storage Serves as Step Towards Printed Memory

Combining nanotech with printed electronics, Duke researchers have created "spray-on" memory that could allow for better low-cost sensing technologies.

Over the past several years, we've seen the introduction of the IoT and a plethora of developmental research for flexible and printable electronics. These fields often intersect with the ongoing research into memory and sensor technologies. With the venues of printable technology expanding, we might finally see a new era in memory storage devices.

Right at those crossroads is Duke University, where researchers have developed a new “spray-on” digital storage which could potentially bring storage devices just about anywhere.

 

Constructing the Device: Nanowires, Nanoparticle Inks, and Polymers

The new “spray-on” technology is a transparent digital memory device that applies a coat of silica-coated nanowire that has been encased in a polymer matrix using just an aerosol jet printer and nanoparticle inks. This is the first time that a memory device has been completely manufactured by printing that is not only convenient but also has practical uses in sensors and RFID. The digital memory also happens to be printed at low temperatures allowing it to have potential applications in flexible programmable electronics.

 

The printed device (left) and the circuit it was used to control, as described below (right). All images used courtesy of Duke University.

 

“Memory is kind of an abstract thing, but essentially it is a series of ones and zeros which you can use to encode information,” said Benjamin Wiley, one of the paper’s authors and associate professor of chemistry at Duke.

The foundation of the printable ink is a nanowire material made of copper and silicon that has the capacity to act as digital information storage. The technology is a bit different from our commonly-used data storage devices in that, instead of using a transistor’s charge to register a zero or one, it encodes data by measuring states of resistance.

This measurement is done by applying a slight amount of voltage to a resistor which can be transitioned between a high resistance that halts the flow of current and a low resistance that lets the current pass through. In addition to this, the polymer and nanowire combination can be dissolved in methanol, which allows a liquid form that can be sprayed onto surfaces.

The device was created by using a nanoparticle ink made of gold to place the gold electrodes onto a slide. The next step was to layer the copper memory material on the gold electrodes, followed by a final layer of copper electrodes.

 

Humble Beginnings: Four Bits of Spray-On Memory in Action

To demonstrate what the device can do, the researchers used an LED light circuit containing four LEDs, where each light would correspond to a high or low resistance which could be programmed to display a specific denotation.

 

 

The device demonstrating the 16 states it can achieve using four bits of memory.

 

This was not the first attempt to manufacture printable digital storage devices, but it is the first to incorporate vital device properties that would allow for practical use.

The spray-on memory is capable of reaching a write speed of just three microseconds, which rivals our current high-grade flash drive speeds. Unfortunately, the spray memory is only capable of storing as much information as a 4-bit drive, which will be upgraded in the future.

However, while currently only able to store small amounts of information, the spray-on memory does have one large advantage over our current memory systems. Typical data storage devices will degrade after about five years, while the spray memory is able to store data for over a decade without degradation while maintaining the ability to rewrite information. The spray-on memory is still in the early stages of development, but further research should increase the storage capacity and potentially replace hard drives in the future.