Researchers Couple Printed Logic with Printed Memory

Print out: The printed transistors on this sheet, made by PARC and Thinfilm, can address an array of printed memory cells.
Thinfilm

The device processes only small amounts of data, but at a very low cost.

Printed electronics have been advancing in bits and pieces for years—a crude processor here, a basic memory device there.

Now researchers at the Palo Alto Research Center (PARC) and the Norwegian companyThinfilm Electronics have announced a printed electronic device that, for the first time, marries transistors with memory. The device provides a low-cost way to read, write, and process small amounts of data. In addition, the added logic increases the amount of data that can be stored.

Printed circuits, made of organic inks, operate far more slowly and with less memory capacity than their silicon counterparts, but they can be made for pennies. Printed circuits can also go where silicon currently cannot: wrapping around a child's toy, for example, or conforming to the curve of a soldier's helmet.

Earlier this year, Thinfilm showed off a handheld device capable of reading cards printed with circuits that store 20 bits of data. In May, the company announced engineering deals with two major toy manufacturers who plan to use its printable memory.

Adding logic to memory is crucial to increasing the storage capacity of the device, explains Janos Veres, manager of printed electronics at PARC. "We really needed to have a printed logic array that lets us address memory and increase bit count," he says. Memory arrays are split up into rows and columns. To select a row or column, you need a logic circuit, Veres says. "The power of this demonstration is we've shown that you can address rows and columns with this technology," he says. "The next step will be building bigger memory."

One of the major advances of this prototype is the development of printed logic circuits that are analogous to so-called CMOS circuits in silicon. CMOS stands for complementary-metal oxide-semiconductor—a combination of two key kinds of transistors, called an n-type and a p-type.