New Ink Could Aid Bendable Displays

U.S. researchers have developed a new type of semiconductor ink that brings companies a step closer to making bendable computer screens or inexpensive sensor tags to help retailers keep track of their inventory.

The discovery lies in the new material — a soluble semiconductor ink capable of carrying a negative electrical charge, said Philippe Inagaki, chief executive officer of Polyera, a specialty chemicals company in Skokie, Illinois, that makes materials for flexible and printed electronics.

In the traditional silicon world there are two fundamental types of semiconductors: P-type, which carry a positive charge, and N-type, which carry a negative charge.

So far, most semiconductor inks, such as one developed by a team at Xerox in 2004, have only been capable of carrying a positive charge, they said. The new ink — developed by researchers at Polyera and BASF SE unit BASF Future Business GmbH and described in the journal Nature — is an N-type.

“When you have both, you make chips and circuits that are faster and more reliable and more energy-efficient. And that’s a pretty big deal,” Inagaki said in a telephone interview.

He said the new semiconductor ink can be printed onto flexible materials, such as a thin film of plastic or even paper, using a modified ink-jet printer.

“What you really want to do is print it like a newspaper,” Inagaki said. “That is really fast and really cheap.”

That would make it possible to print inexpensive radio-frequency identification or RFID tags on most consumer goods, helping retailers keep better track their inventory.

More useful displays you can bend

“This is going to enable the right kinds of printed RFIDs with sufficient performance to be really useful. It will also enable more complicated and useful kinds of flexible displays — displays you can actually bend. And it will enable new kinds of sensor technology,” he said.

In designing the new material, Antonio Facchetti, chief technology officer of the company, said he used techniques similar to those used by drug companies to discover new drug compounds. “You are looking for a new molecule,” he said.

In this case, he developed a molecule that lacks electrons in its core, making it a good transporter of a negative charge. “It carries electrons very efficiently,” Facchetti said.

He said the molecule can be dissolved in a solvent, making it possible to use it as an ink. The company plans to sell it under the brand ActivInk.

Inagaki said the new ink should be fairly easy to manufacture. The hope is that it could be used by electronics companies working to develop devices using this new flexible, printable chip technology.

“We’re at the very early stage of this industry. The first products are just starting to appear,” Inagaki said.

“The potential is to create something as big as the current silicon technology.”

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