Yahoo seems to have swallowed my recent lawsuit post and Ducky's response, claiming E-ink's technology doesn't use suspended particles, but suspended spheres with white halves that reflect light in response to electrical currents. I'm sure he'll enlighten me if I've misunderstood his statements. Here's my take, based on significant time going over the pertinent patents and studying other expert sources.
Like RFI's light valve devices, E-ink's spheres contain particles of colored pigments. E-ink's pigments are coated with silicon-dioxide and mixed with polymers to give them electrical charges and prevent their clumping together. They're mixed in a transparent hydrocarbon-based fluid formulated to disperse them evenly, then mixed with water to form an emulsion.
The drops of emulsion are chemically processed so that polymer shells form around them. They're then adhered to a plastic sheet, making a film that's attached to a layer of electronic circuits.
The white halves of the droplets hold negatively charged white particles, usually of titanium dioxide. The dark halves hold positively charged particles, usually of carbon black or copper chromite. When the circuits apply positive currents, the white particles move to the top of the droplets and the dark ones sink; when they apply negative ones, the dark particles move to the top and the white ones sink.
IOW, the charged pigment particles suspended in E-Ink’s droplets, or spheres, change their position in response to an electrical current, just like the charged pigment particles suspended in RFI's light valve devices. Over the years, E-ink has tweaked the particles to keep them from bunching along the walls of the spheres, but the basic physics are the same.
E-ink is different from SPD in fundamental ways. SPD is a light valve, regulating light passing through. E-ink reflects light. The SPD particles within the film are kept dispersed as evenly as possible. In e-ink the particles are meant to migrate. SPD particles are slender and bi-polar. E-ink particles are spherical and charged either + or -.
I highly doubt that the spherical droplet idea will provide any patent coverage. Spheres are the only obvious shape. Patents have to be non-obvious.
That said, patent decisions are often capricious and irrational. A law firm with the resources can throw a bunch against the wall and see what sticks.