A colour e-reader that supports video and potentially web browsing has been shown off by Dutch researchers.

The prototype uses screen technology - based on century-old science - that its makers say is up to four times more energy efficient than LCD screens.

Once established in the e-reader market, Dutch firm Liquavista hope to see its displays integrated into other devices in the future.

But analysts question whether consumers will be enticed by the greener gadgets.

Liquavista said it expects the first e-readers using the "electrowetting" technology to be available by the middle of 2011 and the technology to then become more widespread.

"You certainly could see this technology in your smartphone, in your mobile phone, in your web tablet, in your PC, in your notebook," said Guy Demuynck, head of the firm.

"But eventually you could see it in your home as your television screen in your living room," he added

Sunshine screen

Electrowetting has been known about for more than a century but is only now being perfected by several companies, for instance, to create auto-focus lenses for cameras.

It involves small electrical charges moving coloured oil within each pixel.

Most current e-readers use e-ink technology - small black and white beads that are manipulated with electrical charges.

Pages on current e-book readers can take up to two seconds to load each page. The new display can change images at a speed of up to 60 times per second, its manufacturers said.

This is fast enough to run video, which typically needs a refresh rate of 50 or 60 frames per second.

Liquavista uses the electrowetting to also add colour to a screen, but unlike liquid crystal displays (LCD) such as those on laptops, it can work without a backlight.

When used in sunlight, the new type of display can bounce the natural light through the oil filters back at the reader.

The brighter the sunshine, the more vivid the screen becomes; when used in a darker environment, the e-reader switches to the backlight automatically.

Johan Feenstra, Liquavista's founder, said the display combines the best of both technologies.

"On the one side there's the LCDs which bring video and colour, as we know from our TV screens. On the other side, there's the electrophoretic displays [e-ink e-readers] which bring low power consumption and readability in all lighting conditions," he said.

The company said the technology is three to four more efficient than LCD screens because of the higher level of backlight passing through each pixel.

James McQuivey, media technology analyst at tech research firm Forrester, agreed electrowetting has the potential to make the transition to devices and public displays such as billboards and bus stop posters.

But, he predicted some obstacles: "The challenge is physics really - it's to get things [oil] to respond quickly enough, and in sunshine - to get enough light to reflect back off the screen."

Green premium?

Despite the novelty of a colour e-readers that play video, the efficiencies of electrowetting may be the factor that holds the greatest potential for this technology.

Eventually, if placed into laptops these screens could deliver battery lives measured in days rather than hours.

"Electricity is not freely available everywhere in developing countries so it means of course if you can run this device for a long time on your batteries," said Mr Demuynck.

He told the BBC that consumers increasingly expect new devices to have low power consumption.

However, Mr McQuivey questions whether people are prepared to pay more for a greener device, where an alternative is readily available.

"Consumers have become spoilt by LCD technology. They are used to charging their devices twice a day and won't pay a huge premium for something that simply doesn't need charging as often," he said.

"So the question is how quickly these new screen technologies can be produced at scale and at what cost," he added.

Liquavista said the manufacturing process is very similar to that for LCDs so existing production lines could be adapted rather than building new facilities.

"That would give it a big advantage over competing new screen technologies like e-ink or OLED which require largely new production processes," Mr McQuivey said.

In the longer-term, Liquavista is exploring other possibilities for the technology with UK e-reader firm Plastic Logic. They hope to produce a flexible colour magazine that can update itself and run video within three years.

There are also a few quick videos at the link. Cool technology.