Graphene membranes may hold the key to low-power color e-paper.

Researchers from the Delft University of Technology in the Netherlands designed graphene-based "mechanical pixels" that could, among other applications, be someday used to enable color IMOD e-paper displays.

In these so-called "graphene balloons", a double layer of graphene (two atoms thick) is deposited on top of circular indents cut into silicon. The graphene membranes enclose air inside the cavities, and the position of the membranes can be changed by applying a pressure difference between the inside and the outside. When the membranes are closer to the silicon they appear blue; when the membranes are pushed away they appear red.

What causes the color change effect is the interference between light waves reflected from the bottom of the cavity and the membrane on top. These reflected waves interfere constructively or destructively depending on the position of the membrane – either adding up or cancelling out different parts of the spectrum of white light. This interference enhances or reduces certain colors in the reflected light. This is basically an IMOD display system, similar to Qualcomm's Mirasol technology.

Source: Graphene-Info