eInk was the third type of alternative display technology that won the mass market, after the CRT and the LCDs (in all their nuances, including OLEDs). It found a niche in the eReader for its very low power consumption. Colour versions have been available but they didn't really succeeded because of the low quality of the colours displayed that are no match for LCDs screen.
Now researchers at Chalmers University of Technology have come up with a new technology that can become the next thing after the eInk. Like eInk it uses very little power, actually ten times less than the power needed by eInk.
The screen is made by a very thin, a few micrometer, electronic reflective paper that can display all colours an LCD screen can. However, being reflective, it can only display a colour if it is present in the light hitting hit: were you looking at the screen in a room bathed by a blue light it could only reflect blue, no other colours are there to reflect. Hence, this kind of screen is perfect under Sun light, there you have all colours available and the plasmonic surface can absorb specific wavelengths and reflect the others.
Differently from an eInk, that can be illuminated from the back, this screen can only work when there is light in the ambient, the brighter (and whiter) the light the better.
The screen surface is layered with nano structures, plasmonic metasurfaces, that can be controlled by applying a voltage, changing their reflectiveness to specific wavelengths. Te nano structures are layered onto a polymer and the whole is extremely thin, thinner than an eInk screen and is bendable.
Provided the ambient light is whitish and bright it can display very bright colours.
The problem, today, is the cost. That is something that can be a game breaker but we know that technology gets cheaper. Yes, some of the materials needed, gold and silver, are expensive, but they are used in such a limited amount that it should not really matter.
Personally, being an intensive user of eReaders, I am looking forward to an electronic book able to display nice colours!