Picture yourself relaxing on a Mediterranean beach, coated in sun screen and reading a trashy novel. You decide the book doesn't take your fancy so you open the back, take out one CD-Rom, pop in another and just as quickly all the text changes giving you a completely new read without having to change the book.

This idyllic scene could be a reality in the next few years following developments at the Media Laboratory, part of the research infrastructure at the Massachusetts Institute of Technology. A team of 10, led by Prof Joseph Jacobson, has created a novel "electronic ink". The ink can change from black to white in response to electrical charges but like any ink can be applied to paper, cloth or just about anything else as a thin film.

This is no fanciful bit of technical whimsy, it has a genuine commercial edge. Prof Jacobson's work is already being commercialised via a new company called E Ink, which has licensed patents from MIT for access to the technology. The company has attracted investment of $15.8 million and is listed in For- tune magazine as one of 12 "Cool Companies" for 1998.

Nor will we have to wait long for results from the company. Prof Jacobson estimated that a "five-year time scale is the right kind of period" for when to expect to see working, marketable products using his research. He detailed his electronic ink research in a recent issue of Nature.

Much work on thin film electronic displays is under way around the world, particularly Japan. Existing technology suffers, however, from being very costly, complex and bulky, Prof Jacobson told The Irish Times. "The whole purpose was to make an ink that you could coat on an arbitrary surface."

The Media Lab team has achieved just that by finding a way to make "microcapsules", tiny spheres which contain white particles floating in a black liquid. The white particles are attracted to a negative charge and so can be pushed to the top or dragged to the bottom of their microcapsule, in turn making it appear white or black.

This sounds simple enough but for the fact that the microcapsules are incredibly small, only one 20th of a millimetre across. This is about the size of a single grain of the toner powder used in a conventional photocopier, Prof Jacobson explained.

One or two or even a dozen microcapsules wouldn't be much good, but put together into an array, they would join to form letters and words, giving the impression of a printed page. The microcapsules are applied like ink to any surface so having an electronic book with flexible pages is well within the realms of reality.

The group has used the technology already to make "some simple displays". There were many uses for this electronic ink, Prof Jacobson said. "I think the book is clearly of interest to us, but you can also think of large signs."

One of the keys of this technology is to achieve a strong contrast between the white and black bits. Liquid crystal displays have reasonable contrast, but this new technology reaches much higher levels of contrast. Prof Jacobson said a page using the ink would look at least as sharp as the printing on a newspaper page.

Another great advantage is cost. The ink is cheap to make and simple to apply. "We designed the chemistry to be based on very low cost chemicals and also a chemistry that is compatible with big scale production." In other words, you can spread it on a book page or on the side of a building to make a billboard without worrying too much about the price. "I believe that the cost of the chemicals is designed to be very low."

The real trick, however, is to develop ways to apply a charge to the ink. Big displays would be comparatively simple because each dot or "pixel" to steal a computing word, could be large. You would require much better resolution for a book page, although the Lab's current technology could support at least 600 dots per inch and this could be pushed to 1,200 dots per inch.

Making a readable page would mean having a "web" of wiring imbedded in the page so that the individual microcapsule dots could be turned white or black to make up letters. All of this can be done either by etching a thin film surface or laying rows and columns of thin wires into a mesh with a microcapsule sitting at each intersection.

Displays and signs are all very well but Prof Jacobson's real aim is to construct a book. One could imagine a one- or two-page display that could be changed as you read through the text, but he is thinking about something much more ambitious, a real electronic book that has up to 200 pages.

"An electronic book is an intriguing possibility," he said. "You would need a display that is incredibly thin and very cheap." His ink applied to plastic or paper sheets could make a multi-page electronic book a reality.

He would prefer having an electronic book with many pages because you could flip forward or back to retrieve data just as you would with a conventional text book. "A book is an excellent interface and you lose some of that if you only have one or two pages."

Much development work is required to interconnect the capabilities of the ink and the electronics to make it come alive, but much of the technology that could make it happen already exists. A fine wire matrix could be made using laser etching or photoengraving as used in electronic circuits and microchips. CDs could be the high volume data store.

The real trick might be finding a way to protect the new electronic books from the ravages of sun cream, sand and sea water.