The higher performance of inorganic devices could also prove useful for organic LED-based displays, says John Rogers, professor of materials science and engineering at the University of Illinois at Urbana-Champaign. Printing techniques are effective at distributing transistors over large areas, which is why they are good for making large displays. Indeed, Rogers suggests printed electronics may ultimately prove most suited to large-area applications.
Kovio’s process was originally based on research by Joseph Jacobson, a professor at MIT’s Media Lab. (See “Print Your Next PC.”) His goal in part was to develop a printing process that used low temperatures compatible with plastic substrates, which could be useful for producing some types of flexible displays. For this he developed inks made with semiconductor nanoparticles that melt at lower temperatures than the bulk form of the semiconductor materials. He cofounded Kovio in 2001, and the company almost immediately went into stealth mode as it developed the technology for commercial applications. But over the years, at the urging of potential customers, the company put more value on device performance than on low-temperature processing. The new methods use higher-temperature processing of the materials after printing–these can still work with a flexible substrate, Subramanian says, but it must be a metal foil, rather than plastic.
The trade-off came in part because of the need to make RFID tags that work with current radio-frequency standards. At first the company could only print radios that worked in the kilohertz range, says Walter Bonneau, a senior vice president at San Diego-based Cubic Corporation, which supplies smart-card systems for major transit systems. But RFID standards demanded megahertz-range devices, he says. Switching to higher temperatures and higher performance devices made it possible to reach the necessary frequencies.
The switch helped persuade Cubic to sign a development and supply agreement with Kovio. (Kovio also announced such an agreement with Toppan Forms in Japan.) The technology could be perfect for replacing magnetic stripe cards, Bonneau says, which are currently used for disposable limited-use passes, with faster, more reliable smart cards. Current contactless smart cards of the type used by frequent travelers on major transit systems can cost as much as $5 a piece to produce. But Kovio’s technology could soon lead to nonmagnetic smart cards that cost a nickel.