According to University of Cincinnati electrical and computer engineer Jason Heikenfeld, there are two types of electronic devices: things such as e-readers, that require little power but have displays with limited performance, and devices such as smartphones and laptops, that display bright, full-color moving video, but that guzzle batteries. After seven years of development, however, Heikenfeld and collaborators from Gamma Dynamics are now presenting a new type of electronic display. They claim that their “zero-power” electrofluidic system combines the energy efficiency of the one type of device, with the high performance of the other.

The main reason that e-readers use so little power is because they utilize reflective, ambient light, just like a newspaper or magazine. Smartphones and their ilk, on the other hand, require an internal backlight, not to mention color filters. The U Cincinnati/Gamma system reportedly allows for bright, color, high-speed images, but does away with the internal light source. Instead, like an e-reader, it uses reflective light. This not only reduces its power requirements, but also lets users see its images in bright sunlight.

The zero-power display consists of a layer of glass, underneath which is a layer of inkjet-like oil and pigment dispersion fluid, followed by a layer of highly-reflective electrodes, and finally another layer of fluid. Ambient light passes through the glass and first layer of fluid, hits the electrodes, and reflects back, displaying the color of the fluid that covers each electrode. An electrical current moves fluid back and forth between the top and bottom layers, to change colors and other image qualities as needed.

Given the high reflectivity of the electrodes, Heikenfeld informs us that even the ambient light available on a street or in a car at night would be sufficient for a zero-power-equipped smartphone. He also suggested that some devices could have a low-power light for use only in complete darkness.

Not only would the system use less power than conventional backlit LCDs, but it would reportedly also allow e-readers to display color and moving video. Existing LCD-manufacturing equipment could be used to produce the technology, which might initially be used in supermarket aisle labels and advertising.

The research was published this week in the journal Applied Physics Letters.