Electronic ink is an attempt to combine the efficiencies of the digital medium with the convenience of paper.  Paper is convenient in that it is extremely light and easily portable.  However, reusing paper usually requires the lengthy and costly process of recycling.  Digital displays, such as an LCD screen, can be easily and instantly reused thousands of time, but the appliance itself is often bulky and awkward to carry around.   Two electronic ink products currently in development hope to wed the advantages of both mediums and eliminate the drawbacks.

Gyricon, in development at Xerox Palo Atlo Research Center (PARC), is a thin layer of transparent plastic.  Imbedded within the plastic are millions of tiny beads floating in oil-filled cavities.  The beads contain two hemispheres of contrasting colors, such as black and white, each of which is either positively or negatively charged.  When a voltage is applied to the Gyricon sheet, the floating beads rotate in response to the electrical charge, displaying either their black or white side.  It is this combination of tiny black and white dots that creates the text on the page.  With each electrical charge, the text formed on the page changes as the beads rotate between black and white.

            
close-up look at several thousand Gyricon beads

Xerox proposes that the electrical charge could be applied to the sheet through printer- and wand-like devices.  Another idea is to bound several Gyricon sheets together into a "book" with the necessary electrical components stored in the spine.  See  http://www.parc.xerox.com/dhl/projects/gyricon/  for more information and additional pictures of the Gyricon technology.

The technology for Immedia was originally created in MIT's Media Labs.  The E Ink Corporation has been founded in order to bring this technology to the market place.  Similar to Gyricon, at the base of this technology are millions of beads.  Unlike Gyricon, however, the beads reside in a liquid ink that can be applied to almost any surface.  The beads are white, but float in a dark dye.  When an electrical charge is applied, the white beads float to the surface creating a white dot.  The absence of any electrical charge causes the beads to float below the dark ink, forming a black dot.