# This hard drive is just 100 nanometres wide

My house is full of old hard disk drives. Because these date back to the late 90s and early 2000s, they take up a lot of space to hold very little data, but I can’t bring myself to chuck them out, somehow. This would be far less annoying if they used which has created a hard disk just 100 nanometres across.

True, that hard disk can hold a single kilobyte of data – that’s about 1/500th of an average JPEG picture – but you have to appreciate the scale we’re talking here. One hundred nanometres is so small it can fit through a surgical mask, and around half the size of the Mycoplasma bacterium. So while one of these microscopic storage units can hold a single kilobyte, chain a bunch together and you’ve got something far more efficient than our current storage methods.

To put that into some context, our most efficient storage at the moment offers a capacity of around one terabit per square inch. This is 500 terabits per square inch. Or as Sander Otte from Delft University explains: “In theory, this storage density would allow all books ever created by humans to be written on a single post stamp.”

How does it work? Like a sliding puzzle, according to Otte. “Every bit consists of two positions on a surface of copper atoms, and one chlorine atom that we can slide back and forth between these two positions,” he explained. “If the chlorine atom is in the top position, there is a hole beneath it – we call this a 1. If the hole is in the top position and the chlorine atom is therefore on the bottom, then the bit is a 0.” Because each chlorine atom is surrounded by other chlorine atoms, they keep each other neatly in place.

That’s pretty brilliant on its own, but this visualisation from the university breaks down exactly how clever it is:

Sadly, the technology is stuck in the laboratory for now. The chlorine and copper atoms only remain stable in a clean vacuum and at a chilly 77 kelvin. If it gets any warmer – and I’m going to assume your house is warmer than the temperature of liquid nitrogen here – then the data is lost as the atoms lose their tight organisation. It still remains hugely promising research, and it will be fascinating to see where the technology goes next.

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