Now researchers at the Palo Alto Research Center (PARC) and the Norwegian company Thinfilm 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.
The prototype is a “building block” that can be used for a number of different applications, says Raghu Das, CEO of IDTechEX, a research firm. “There has been a huge effort on printing transistors globally,” Das says, “but very poor effort on making useful building blocks like this, which can be used horizontally for many applications.” The announcement by PARC and Thinfilm, he says, is “very good news.”
Thinfilm CEO Davor Sutija is interested in integrating the new device with a number of other printed electronics, particularly sensors. “You can see if a sensor has hit a particular threshold and record the number of times in memory,” he says. Sutija says the technology could record if a vaccine has been exposed to incorrect handling practices, or if food or other items that need refrigeration have gotten too warm. It could also power price tags that change depending on the time of day.
These sorts of applications are only possible, however, if manufacturing costs can be kept down. Thinfilm has partnered with Inktec, a leading developer of inks, to make the logic and memory devices in bulk. According to Sutija, his company’s 20-bit memory sells for five cents. Within the next three to five years, he expects, the more advanced systems will cost pennies. “Three to six cents isn’t hard to envision, given the scalability of printing,” he says.