What will become store data on CD, DVD, hard drives, memory cards or USB keys? They will disappear sooner or later, it is a certainty. The problem has long been known, leading to distinguish storage, short-term recording, archiving, to keep permanently valuable data. When it comes to keep records over long periods, for regulatory reasons, for example, as is the case in aviation or in hazardous industries, including nuclear.
Our ancestors used the paper or parchment, and even further away from us yet, etching and painting on the rock. Today, the classical solution is the microfiche or microfilm, that consist of photographing the document. An analogic principle, therefore. Digital seems to run out for the long term …
“Digital technology is wonderful but is not secure,” concludes Alain Rey, one of the founders of the company Arnano, spin-off from CEA-Leti. His company has made as an original specialty using a laser to burn holographic and microscopic patterns, to the micrometer scale, on hard surfaces, like glass or sapphire. The company works especially for the watch industry to include authentication codes, such as invisible logos to the naked eye. The principle of laser burning eliminates masks in microelectronics, very expensive and that are reserved for mass production.
This storage disc is burned in a similar way. A synthetic sapphire surface (transparent), 0.7 mm thick, is coated with titanium nitride, “which serves as ink,” says Alain Rey, and the laser is used to draw the patterns. Then a second disc of sapphire is applied over. After heating, there is a kind of molecular bonding and the two plates are fused together, linked in the same crystal lattice. “Sapphire is just a little less hard than diamond. It is solid, it resists all chemicals and holds heat up to 1,700 ° C.” He added that the disc don’t fear rodents, unlike microfiches.
The final shape is a disc, but it is not a DVD. The circular shape with a diameter of 200 mm, is just the initial form of synthetic sapphire ingots but also that of microelectronics machine tools, adapted to silicon wafers. Needless to slip it into a DVD reader!
For coding, it is the analog that was chosen. Digital technology suffers of three digital obsolescence:
– The media first. CDs and DVDs are short-lived means, 3 to 10 years.
– The tapes, 30 years.
– The software then. A text written in Word 1 will be hard to be read for our nowadays softwares, for example.
Similarly, CD and DVD encoding, very efficient, use complex algorithms, which can correct errors. But all of this is based on proprietary techniques, which change over time. As back up material, we use the sapphire, which is unalterable. For the recording, we use the analog documents that are images, just reduced in size. There is no coding. To read them, just need to enlarge them! Whatever the technique they will use, our descendants will be able to do so.
For now, the reading can be done with a small microscope that plugs into a computer, with a high resolution camera equipped with a zoom or with a special scanner that will provide files, text or images.