Sticky nanowire tapes that sense, translate and transmit data wirelessly

London, July 29 : A tape, much like the common sticky tape, that can carry out humongous electronic tasks like active sensing, data translation, and wireless transmission may soon be on the anvil.

Made by growing a mixed "lawn" of two kinds of nanowires, such cheap, high-quality image sensors may have uses that cannot be conceived using today's more expensive technology, said researchers who developed this technology.

Today sensors, such as those found in digital cameras, are made like any other silicon chip - they are carved out from a block of material. However, the new nanowire sensors are instead built from the bottom up, by using chemically-grown nano-sized components.

Led by Ali Javey, at the University of California, Berkeley, the researchers developed the process, by first growing an unruly "lawn" of nanowires on a surface. Later the crop is printed onto another surface, which also tidies them up simultaneously.

"At the first stage, the nanowires are more-or-less standing up, like a bad hair day. But during the printing process, they effectively get combed," New Scientist quoted Javey, as saying.

Nanowires are a few tenths of a millimetre long and a few tens of nanometres wide, which can be printed onto anything from silicon to plastic or paper. One must keep in mind that they must be prepared with a pattern that guides the nanowires to predetermined locations, no matter what the surface is like.

For making the functioning sensor, two different "crops" of nanotubes are printed onto the same surface. While cadmium selenide nanowires produce electric charge when hit by light, sensors made from silicon-coated germanium act as transistors to amplify that charge.

Researchers had built a prototype sensor with 260 pixels, each made from up to 5 sensor nanowires for each transistor nanowire and it was found that 80 percent of the sensor circuits worked positively.

"It's the largest integrated device to date based on nanowires," said Javey.

He said that the arrays are reliable, flexible and easy to scale up and now he hopes to grow self-powered, wireless versions on rolls of tape several metres in diameter.

"Imagine having a tape - just like your sticky tape - that you can grab and put on anywhere you want. This tape will have all the needed components to do the active sensing, translate the data, and transmit it wirelessly," he said.

Javey also said that producing image sensors in large, cheap areas may initiate new uses for imaging to emerge. Right now the researchers are working on the extra parts needed: nano-scale batteries for power and equally small wireless components.

John Rogers, a specialist in organic electronics at the University of Illinois at Urbana-Champaign, said that Javey and colleagues are among the very first to successfully demonstrate that electronic devices can be assembled by chemically growing nanowires from the bottom up.

"I really like what they have done here," he said.

Zhong Wang, who leads a nanotechnology group at Georgia Institute of Technology, Atlanta, Georgia, added: "It demonstrates an outstanding application of nanowires in integrated eectronics."

ANI