Magnetic bacteria create a biological hard drive

COMPUTER virus destroyed your hard drive? Don't worry, some day bacteria might build you a bigger and better one.

Hard drives store data on discs coated with a metallic film divided into tiny magnetic regions, each of which stores a single bit - the more regions you can squeeze on to a disc, the bigger the capacity. Now, a team at the University of Leeds, UK, have borrowed a trick from nature to build a new kind of hard drive.

Certain strains of bacteria absorb iron to make magnetic nanoparticles that let them navigate using the Earth's magnetic field. The team have extracted the protein behind this process and used it to create magnetic patterns that can store data. "We're using and abusing nature because it's had billions of years to do all of its experiments through evolution, so there is almost no point in us starting from scratch," says Sarah Staniland, who led the research (Small, vol 8, p 204).

Hard drives are usually made by "sputtering", in which clouds of argon ions are fired at a sheet of magnetic material, knocking off particles which are deposited as a thin film on a disc. Groups of these particles, called grains, form the magnetic regions on the drive, with around 100 grains corresponding to one bit.

Instead of granular media, Staniland's team produce bit-patterned media. They start with a gold surface coated in chemicals in a chessboard pattern so that one set of squares binds proteins and the other repels them. They then apply the magnet-producing protein and coat the surface with an iron solution, which the protein-covered squares convert into magnetic material.

As the name suggests, each magnetic square in bit-patterned media can store one bit. Each square Staniland's team have so far produced is around 20 micrometres wide, far too bulky to store data with a density comparable to today's hard drives. She says they now plan to test out nano-sized squares, 1000 times smaller and much closer to existing drive density.

Eventually, she hopes to create a hard drive with a single iron particle per square, which will store as much as 1 terabyte of data per square inch - far beyond the capability of most hard drives.

"They've done nice work showing how you can make particles on a surface," says Thomas Thomson, who studies data storage at the University of Manchester, UK. "But it is some distance away from what you would need if you were seriously contemplating it as a product."


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