And because it is flexible, it will let you copy just about anything, even if it's on a curved surface such as an open book or the label on a wine bottle.

The lightweight device, unveiled last week at an electronics conference in San Francisco, is the latest development in the field of flexible organic electronics, which exploits the electronic properties of conducting plastics. Light-emitting plastics are already being used in flexible computer displays, and organic LED-based TV screens are in development.

But the new flexible scanner is using light-sensitive organic components instead of light-generating ones.The new device, developed in Japan by electrical engineer Takao Someya and colleagues at the University of Tokyo, comprises a polymer matrix in which thousands of light-sensitive plastic photodiodes have been deposited 700 micrometres apart beneath a grid of plastic transistors.

Each photodiode produces a current in response to light input, which its accompanying transistor stores as a charge. This can then be read into the memory of a mobile phone and converted into an image.To use the sheet image scanner, it has to be placed on the area of interest, such as a bottle or an open book.

It can only capture the image it covers; it cannot be swiped across it like an office hand scanner. The plastic is transparent, so ambient light can pass through it to reach the object being scanned.

Because the transistors sit on top of the diodes, shielding them from ambient light, only the light that reflects off bright areas strikes the photodiodes, which generate a current proportional to the greyscale light intensity. The resulting charges are stored in the array of transistors and are then read out to construct an image.

The developers say their device can scan text with resolution good enough "to image all the letters on a wine bottle". In their prototype the resolution is only 36 dots per inch, but the plastic electronics are scaleable and 250 dpi is said to be easily achievable.

Someya says it could be on the market in three years with sizes varying up to A4. A 7-centimetre-square scanner, small enough to fit in a wallet, will cost about $10, he predicts. So far, Someya has only gotten images out of the scanner using complicated benchtop electronics.

He says his next step will be to develop a custom chip that will read out the data and feed it into a mobile phone, or to a USB keyring-like storage device for viewing later on a computer.

He envisages making a colour version of the scanner, using an array of red, green and blue-sensitive cells, though with lower resolution. Someya says the sheet image scanner will offer a better way to acquire an image than using a cellphone camera because it can acquire a higher resolution image from oddly shaped surfaces.

"For example, it will be able to accurately capture images of fine patterns drawn around the pillars on historic buildings," he says.

This article appeared in the Dec 25 edition of New Scientist.

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