Hold a second, dear casual reader. You’re probably aware that ‘knowledge crystals’ or ‘data crystals’ or ‘memory crystals’ (and the like) are rather common sci-fi tropes. What you may not know is that this kind of tech has been in development for a while now. So memory crystals have been around for a while. So why can’t you just pitch up to your favorite electronics store and get your own memory crystal? Place some very important data on a piece of jewelry, maybe using a gemstone in a ring to open up a portal (yeah, right – it’s just the door to your apartment), yeah? We here at science.casual suspect that it’s likely because while there have been proof-of-concept studies where they prove that something actually works – and there’s been quite a few of those here in this blog (just look for anything tagged with #materials) – it’s another thing to scale it to production. In other words, it works and it’s probably expensive.
There’s also another thing to consider – consumers are more likely to buy data storage that is rewritable. Some of you readers might be old enough to remember and even have (and might even still) CD-Rs. To some of you younger readers, these were CDs in which you could record data onto it, but only once. It was the next evolution from the mixtape that used actual cassette tapes. Some of us who knew how to dance (and had friends that dance and let us not discuss that any further) had our own mixtapes, Trevor Noah revealed in his autobiography that he made a business of it in his younger days, but face it – most of us used it for love songs.
The problem was obvious – you could only record once. You could only imagine that we lost our minds when CD-RWs came out. Considering that so much data is generated per day, we may not need permanent solutions. Sometimes we need temporary storage, but you can only imagine how much of a pain it’s going to be when you have to sift through a sack of crystals to find the one where you saved that expenses report from 4 years ago, hoping that you didn’t leave it on the grounds of Raven’s Ghyll as you made your escape from Claude d’Orsay (but chances are you left it in the bathroom at Starbucks). One would imagine that it’s probably not easy to rewrite a crystal itself; it just seems so permanent. That’s where Riesen et al. step in – in this week’s Featured Article (and thank you for hanging on through the lead-up to this point, geez), they propose that crystals can indeed be used as a rewritable medium for data storage.
Think back to the last time you took a chemistry class – remember precipitation reactions? You added this clear liquid to another clear liquid and a solid forms or you end up with this foggy-looking liquid (which means you do have solid, it’s just very fine and easily dispersed in water, kind of like milk), remember that? Would you believe that this is also the same method that the authors used to make their crystals, albeit using much more sophisticated and precise (so really expensive) techniques? They got very tiny nanocrystals out of it, which gives you an idea of their size. To test out how this worked, they used a rather complicated laser/microscope setup similar to DVD players (hey, they’re already thinking of us who might be buying this!) in order to read the crystals. UV lasers, specifically in the UV-C range, were used to write the crystals.
OK, we know this works (because otherwise it wouldn’t have made it to print), but how did the authors conclude that? Certain particles (specifically samarium ions) change their oxidation state, which mainly has to do with how many electrons are around the nucleus, depending on what energy they absorb. The UV lasers take care of that in this proof-of-concept study; by changing the states of some of the particles, they ‘write/re-write/erase’ data by switching the oxidation states of the samarium particles. This is really not unlike how data is already read and written anyway. The authors attest that the amount of data that may be read/written in a single nanocrystal depends on the amount of samarium ions as well as eliminating background light, so my idea of using a diamond (or some crystal) ring to enter an apartment could use some work. One would imagine that really high-end hotels might jump on this kind of tech just for the glitz-and-glamour factor.
One would imagine that since these are nanocrystals, you wouldn’t need so much energy to read/write them (which is good – more energy means more expensive, and you can imagine it will eat through your batteries quickly). According to the authors, a sample of nanocrystal would only require energy in the femtojoule range. If you can’t picture that since it’s just that small, think about how much energy (you clicked on the link in this sentence, right?) you need to lift a tomato up to about your waist. Take that energy and divide it by one quadrillion (or one million billion, or one followed by fifteen zeroes). It has the potential to cram a lot of data into it as well, somewhere in the terabyte to petabyte range per cubic centimeter. Imagine that, all the digital data produced in all the world produced in one day, which is about the same as how much digital data was produced in all of 1995, could be saved in a crystal about as big as playing dice.
Holding all the world’s knowledge in a d20? Tabletop RPG nerds would be having fits at the idea of owning their own lore crystal. I’d be one of the first.
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Featured Article: Riesen N, Pan X, Badek K, Ruan Y, Monro TM, Zhao J, Ebendorff-Heidepriem H, Riesen H. (2018). Towards rewritable multilevel optical data storage in single nanocrystals. Optics Express 26(9): 12266-12276. DOI: 10.1364/OE.26.012266.
Featured Image: Public Domain (Author: PublicDomainPictures, 2014)