Wearable electronics: NASA develops memory-storing e-textile material

Resistive memory used in e-garments

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At its most basic, the e-textile is formed from a lattice of copper wires. The top copper wire is left bare, the bottom wire is coated in copper oxide, and at each intersection is a small piece of platinum. The data is stored in the copper oxide coating by a process that is called resistive switching, and if you understand how a transistor works, just think of the copper oxide as the dielectric layer. The read/write process is also much the same as normal RAM: a high voltage (3V in this case) is used to write bits, and a low voltage (0.5V) reads bits.

The total capacity of copper/platinum/copper oxide resistive memory is defined by the number of intersections, so in the image above, the piece of memory being held between two (rather luminous) fingers would store just 28 bits of data. In this case, though, the researchers used copper wire that is 1 millimeter thick — but there’s no reason that it couldn’t be scaled down to just a few nanometers… and in that case, the capacity of an e-garment could be measured in gigabytes or terabytes.

Copper oxide/copper/platinum resistive memory

In terms of performance and volatility, NASA’s copper oxide-based memory is surprisingly tenacious: this early prototype should be able to store data for over 115 days (and the bits can always be refreshed before they die!) — and data can be read and written with a 60 microsecond (60 millionths of a second) pulse. From a tailoring perspective, in case you were wondering, the “weave” of the wires make this memory an ideal base for other threads, such as cotton or synthetics — and it also makes the memory flexible, a key point when discussing smart fabrics and wearable electronics.

There are technical constraints, however. All of those wires have to run to a controller somewhere, and they have to be powered by some kind of battery. The practical constraints are even more taxing: What happens if someone punches you and breaks some wires? Do you lose the data? If you step into direct sunlight and heat up your e-vest, will the data lose its integrity? Wouldn’t a suit made out of copper be rather heavy?

Those problems can be surmounted, though, and the pay-off of successfully creating an e-garment would be monumental. NASA’s memory could enable wearable sensors for people with medical conditions, or even as an early-warning system for healthy people. You wouldn’t need a whole suit, either: a small one-square-centimeter patch, assuming 50nm gaps between wires, could store over a gigabyte — and in that space you could store vital contact information, music, documents, software…

Stepping even further outside the box, don’t forget that this memory could be used in any kind of textile. Imagine a mug or plate or desk with built-in memory. Everything you touch and interact with could be smart. Curtains could remember if you like them being up or down. A chair could learn from the backsides of its occupants and rejig its shape, depending on weight and distribution…

Read more at AIP Advances (research paper), or about resistive memory

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