The creation of a new “spray-on” digital memory device, produced using just an aerosol jet printer and nanoparticle inks, could take us a significant step forwards toward a future of low-cost, flexible electronics. Acting like a USB flash drive, the new device is part of the rising wave of printable electronics.
The “spray-on” device, with a capability similar to that of a 4-bit flash drive, is the first fully-printed digital memory that would be suitable for practical use in simple electronics such as environmental sensors or RFID tags. Moreover, due to being jet-printed at comparatively low temperatures, it is possible to use in the building of programmable electronic devices on bendable materials like paper, plastic or fabric.
“We have all of the parameters that would allow this to be used for a practical application, and we’ve even done our own little demonstration using LEDs,” said Duke graduate student Matthew Catenacci, who describes the device in a paper published in the Journal of Electronic Materials.
Roughly the size of a postage stamp, the device’s core is a new copper nanowire-based printable material that is capable of storing digital information. Made of silica-coated copper nanowires encased in a polymer matrix, the material encodes information in states of resistance, as opposed to the more usual states of charge.
With a small voltage applied to the material, it is possible to switch it from a state of high resistance, stopping any electric current, and one of low resistance, allowing current to flow. Moreover, unlike the silicon that largely dominates modern electronics, the nanowires and polymer can be dissolved in methanol, creating a liquid that can be sprayed through the nozzle of a printer.
“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, an associate professor of chemistry at Duke and an author on the paper.
“Most flash drives encode information in series of silicon transistors, which can exist in a charged state, corresponding to a ‘one’, and an uncharged state, corresponding to a ‘zero’.”
While not the first of its kind in regards to printable memory devices, the key importance of the new device is its practicality. The write speed is around three microseconds, rivalling the speed of flash drives. Additionally, tests found that written information may be retained for up to ten years, and the material can be re-written many times without degrading.
Although the memory currently available on the device is too small for storing anything like music files, the low cost and flexibility hold a lot of potential for applications such as RFID tags. Currently limited to just encoding a particular produce number, smarter RFID tags using the device could sense their environments and record the state over time.
In and of itself the device is not currently set to radically change electronics. It could however, be the gateway to a new generation of printed devices.