Retro RAM

In a throwback to the bulky electromechanical computers of the 1940s, future memory chips might harbor moving parts, gently nudging each other. This time, data would be stored by billions of carbon nanotubes acting as mechanical switches.

MEMORY PALACES. Electrostatic repulsion from an electrode (drum on lower right) pushes a carbon nanotube to touch and charge the metal coating on a second nanotube, storing a data bit. Nature Nanotechnology

Gehan Amaratunga of the University of Cambridge in England and his collaborators grew pairs of 60-nanometer-wide nanotubes standing vertically at prescribed spots on a silicon chip. They left one of the nanotubes in each pair naked, while coating the other one with an insulating and a metallic layer. They then put a positive voltage on the naked nanotube through an electrode at its base.

Another electrode lying next to it, also at a positive voltage, electrostatically repelled the naked nanotube, pushing it to touch the coated nanotube. Once voltage was removed, the naked nanotube sprang back, leaving positive electric charges on the coating of its mate—and switching a data bit from 0 to 1.

Compared with current RAM chips, which switch bits “on” using silicon-based electronic transistors, memory based on such mechanical switches might pack in similar amounts of data while producing only half as much heat, Amaratunga says. That’s because silicon transistors tend to leak electrons even in their “off” position. “But here, you physically break contact,” he says. Less waste heat means better energy efficiency, and—for laptops—longer battery life. The results appear in the January Nature Nanotechnology.

Amaratunga says that the technology should be relatively straightforward to add to current chip fabrication and that, if developed for mass production, the chip could be ready to commercialize within 5 years.

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