Researchers at the California Institute of Technology have created a memory circuit the size of a white blood cell that they claim has enough capacity to store the Declaration of Independence and still have space left over. The circuit, built by a joint Caltech-UCLA team, has a 160-Kbit capacity -- reportedly the densest memory circuit ever fabricated.

James Heath, a Caltech chemistry professor who led the research team, called the creation of the memory circuit a milestone in manufacturing, even though it's nowhere near ready for wide-scale production and sale.

"It's the sort of device that Intel would contemplate making in the year 2020," says Heath. "But at the moment, it furthers our goal of learning how to manufacture functional electronic circuitry at molecular dimensions."

Caltech researchers say the 160,000 memory bits in the circuit are arranged like a large tic-tac-toe board -- 400 silicon wires crossed by 400 titanium wires -- with a layer of molecular switches sandwiched in between. Each wire crossing represents a bit, and a single bit is 15 nanometers wide. That's one ten-thousandth of the diameter of a human hair. In comparison, they add, the densest memory devices currently on the market are about 140 nanometers wide.

"Whether it's actually possible to get this new memory circuit into a laptop, I don't know," says Heath. "But we have time."

The researchers' work appears in today's issue of the journal Nature.