Kindle and other
e-readers have
created a tipping
point for e-paper,
but consumers will
also want video
capabilities, bistable
pixels, and thin or
flexible displays, says
Jason heikenfeld.
shortly anyone on the globe can selectively download books from a library of
millions,” he says. However, even with
the promise of so much content, potential buyers may put off purchasing
e-readers until the displays can support
desktop-quality color in devices that do
not cost as much as a tablet PC.
Kars-Michiel Lenssen and his team
at Philips Research in Eindhoven,
Netherlands, are working to solve this
problem. Lenssen, who is director and
principal scientist at Philips Research,
started the color e-paper project several years ago with the goal of making
low-power, color e-paper brighter than
is currently possible. “We believed that
electronic paper would enable new applications, but we also realized that
bright colors would be required for
a really broad market acceptance in
the future,” Lenssen says. “That’s why
Philips decided to start a dedicated research project on this topic.”
Philips’ technology, called in-plane
electrophoretics, is different from E
Ink’s electrophoresis technique. With
the electrophoresis technique, used in
the Kindle and other popular e-readers, an electric field controls titanium
dioxide particles that are suspended in
capsules. By applying an electric current, the particles can be forced to the
top of the capsules. When the particles
are near the display’s surface, the display appears white because light is reflected or scattered. When the particles
are farther away from the surface, the
display appears dark because light is
absorbed. By selectively making certain areas light or dark, fonts and images can be rendered on the display.
Lenssen’s in-plane electrophoretics technique, in contrast, relies on
two particle-filled capsules for each
pixel, one containing yellow and cyan,
the other magenta and black. By controlling voltages, the colored particles either spread across the pixel or
move out of sight altogether, making
it possible to render different colors
by controlling the number of colored
particles shown. To create white, the
particles simply shift to reveal the
white substrate beneath the capsules.
With in-plane electrophoretics research now maturing, Lenssen and
his team are exploring several applications for the technology, with the next
step being to bring the technology to
production in real-world products.
Lenssen says he is looking beyond
e-readers as the primary application.
“We think there is more potential,
particularly when bright color e-paper
will be available,” he says. “For example, replacing printed paper signs in
retail with electronic paper could save
a lot of money not only on printing
costs, but also on distribution costs
and labor costs for installing and replacing signs.”
Besides display-type applications,
such as e-readers and digital signage,
Lenssen says there are many other opportunities for in-plane electrophoretics, such as digital surfaces on which
color could be changed electronically.
Such surfaces, which Lenssen calls
“digital paint,” could be used, for example, as electronic skins for consumer devices. Instead of physically
exchanging a device’s skin with one of
a different color, a user could electronically choose his or her preferred color
for each occasion.
“Our e-paper technology could also
enable patterns that appear on the
electronic skin of a device like a kind
of electronic tattoo,” he says. “
Chameleons and cuttlefish are inspiring examples from nature in this respect.”
electrofluidic Display
Another approach to the problem of
low-power, high-quality color in e-paper comes from the Novel Devices
Lab at the University of Cincinnati.
The technology, called electrofluidic
display, uses voltage to manipulate colored inks in much the same way that
print heads operate in color printers.
Jason Heikenfeld, a professor of electrical engineering at the University of
Cincinnati and head of the Novel Devices Lab, formed Gamma Dynamics
LLC earlier this year to create products based on his electrofluidic display
technology. He and his colleagues are
considering a wide range of applications, from e-readers to e-windows to
tunable casings for electronic devices.
“One challenge,” he says, “is picking a
first target application out of so many
opportunities.”
Heikenfeld says the Kindle and
other e-readers have created a tip-
Jason heikenfeld, head of the novel Devices Lab at the university of cincinnati, is working on
electrofluidic display technology based on a process involving pigment dispersion.
