Out of the Lab: First Tans, Now Storage: Spray-On Storage Holds Promise for IoT

Out of the Lab: First Tans, Now Storage: Spray-On Storage Holds Promise for IoT

When we think about IoT, it’s usually in terms of networks composed of computing devices and networks. But what about storage? Even the smallest of sensors and control points require storage, yet most IoT design neglects the need for local storage. Part of the reason: It’s been expensive and difficult to embed storage into materials–until now.

Spray-on storage circuit (Source: M. Catenacci, Duke University)

Thanks to a new material developed by researchers at Duke University, storage for IoT nodes may involve spraying on nanoparticle inks to surfaces such as paper, plastic, and fabric–making it possible to embed digital information directly onto devices like groceries, clothing, and furniture.

Printable memory devices aren’t new, but the big advantage of the new material developed by the Duke researchers is that the printing material uses off-the-shelf technology (standard aerosol inkjet printers) and doesn’t require high heat, which would make it impractical to apply to fragile substances. Moreover, the “wire speed time”–the time required to change states–of the Duke approach is faster than that of current approaches. At three microseconds, it’s in line with the speed of flash drives. Researchers also estimate the written information will last for about ten years, and can be re-written and over-written multiple times without degrading.

The printing material consists of silica-coated copper nanowires encased in a polymer matrix, which can be dissolved in methanol to create nanoparticle “storage ink” that a printer can spay on. Applying a small voltage (via off-the-shelf electronics)  to the material switches it between a state of high resistance to a state of low resistance. Electronics can subsequently interpret the pattern of high and low resistance as states corresponding to particular symbols. (For instance, high resistance can be interpreted as a binary “one” and low resistance as “zero”, or vice versa).

The Duke researchers, specifically Matthew Catenacci, the graduate student who spearheaded the research, created a simple prototype printable memory device. Catenacci first printed  commercial nanoparticle ink to create a series of gold electrodes on a glass slide. He and his team then printed the copper-nanowire polymer over the gold electrodes, and applied a second set of copper electrodes. Then they wired this device–which is about an inch square–to a circuit containing four LED lights, creating a possible 16 states.

This obviously isn’t much–16 states won’t even store the whole of the Latin alphabet–but it’s a highly promising start. These devices could ultimately store information such as a timestamped temperature record of an item (to ensure it has never been exposed to out-of-range temperatures) or capture simple sensor measurements.

The bottom line? It’s early days, but watch this space. Embedding storage into manufactured devices for use by IoT networks may soon be as commonplace as tagging retail items with bar codes.

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