“In the last few decades there’s been a steady, exponential increase in the amount of information that can be stored on memory devices, but things have now reached a point where we’re running up against physical limits,” said C. Grant Willson, professor of chemistry and biochemistry in the College of Natural Sciences and the Rashid Engineering Regents Chair in the Cockrell School of Engineering.
“The industry is now at about a terabit of information per square inch,” said Willson, who co-authored the paper with chemical engineering professor Christopher Ellison and a team of graduate and undergraduate students. “If we moved the (magnetic storage) dots much closer together with the current method, they would begin to flip spontaneously now and then, and the archival properties of hard disk drives would be lost.”
There’s a quirk in the physics, however. If the dots are isolated from one another, with no magnetic material between them, they can be pushed closer together without destabilization. This is where block copolymers come in. At room temperature, coated on a disk surface, they don’t look like much. 
But if they’re designed in the right way, and given the right prod, they’ll self-assemble into highly regular patterns of dots or lines. If the surface onto which they’re coated already has some guideposts etched into it, the dots or lines will form into precisely the patterns needed for a hard disk drive.