Growing a mixed 鈥渓awn鈥� of two kinds of nanowires can make a new kind of light-sensing array that could be made in metre-scale sheets. The researchers behind the prototype say such cheap, high-quality image sensors would allow uses not conceivable using today鈥檚 more expensive technology.
Current sensors, such as those found in digital cameras, are made like any other silicon chip 鈥� they are carved out from a block of material. The new nanowire sensors are instead built from the bottom up, using chemically-grown nano-sized components.
A research team led by , at the University of California, Berkeley, developed the process. They start by growing an unruly 鈥渓awn鈥� of nanowires on a surface.
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The crop is then printed onto another surface, a step that simultaneously tidies them up.
鈥淎t 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,鈥� says Javey.
The nanowires, which are a few tenths of a millimetre long and a few tens of nanometres wide, can be printed onto anything from silicon to plastic or paper. Whatever the surface, it must be prepared with a pattern that guides the nanowires to predetermined locations.
To make the functioning sensor, two different 鈥渃rops鈥� of nanotubes are printed onto the same surface. Cadmium selenide nanowires produce electric charge when hit by light, while those made from silicon-coated germanium act as transistors to amplify that charge.
Proof of concept
The team built a prototype sensor with 260 pixels, each made from up to 5 sensor nanowires for each transistor nanowire. In tests, 80% of the sensor circuits worked as desired (see image, right). 鈥淚t鈥檚 the largest integrated device to date based on nanowires,鈥� Javey says.
Javey says the arrays are reliable, flexible and easy to scale up. He envisions growing self-powered, wireless versions on rolls of tape several metres in diameter.
鈥淚magine having a tape 鈥� just like your sticky tape 鈥� that you can grab and put on anywhere you want,鈥� he says. 鈥淭his tape will have all the needed components to do the active sensing, translate the data, and transmit it wirelessly.鈥�
Producing image sensors in large, cheap areas could encourage new uses for imaging to emerge, says Javey. His team is working on the extra parts needed: nano-scale batteries for power and equally small wireless components.
鈥淥utstanding application鈥�
Javey and colleagues are among the very first to successfully demonstrate that different kinds of nanowires can be brought together to make integrated sensor circuitry, says , a specialist in organic electronics at the University of Illinois at Urbana-Champaign. 鈥淚 really like what they have done here,鈥� he told New 杏吧原创.
, who leads a nanotechnology group at Georgia Institute of Technology, Atlanta, Georgia, added: 鈥淚t demonstrates an outstanding application of nanowires in integrated electronics.鈥�
Journal reference: ,
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