A step closer to rollable, foldable e-Devices

2nd November 2012

The next generation of electronic displays is a step closer thanks to research from the University of Cincinnati.

 

 

Advances that will eventually bring foldable/rollable e-devices, as well as no pixel borders have been experimentally verified and proven to work in concept at UC's Novel Devices Laboratory. The research was published this week in the journal Nature Communications.

The study, "Bright e-Paper by Transport of Ink through a White Electrofluidic Imaging Film" is authored by Matthew Hagedon, Shu Yang and Ann Russell, as well as Jason Heikenfeld, associate professor of electronic and computing systems. UC worked on this research with start-up company Gamma Dynamics.

Electrofluidic imaging film

One challenge in creating foldable e-Paper devices has been the device screen, which is currently made of rigid glass. But what if the screen were a paper-thin plastic that rolled like a window shade? You'd have a device like an iPad that could be folded or rolled up repeatedly – even tens of thousands of times.

The research this week experimentally verifies that such a screen of paper-thin plastic, referred to as "electrofluidic imaging film," actually works. The breakthrough is a white, porous film coated with a thin layer of reflective electrodes and spacers. These are subjected to unique and sophisticated fluid mechanics in order to electrically transport the coloured ink and clear-oil fluids (text, images, video) of electronic devices.

According to UC's Hagedon, "This is the first of any type of electro-wetting display that can be made as a simple film that you laminate onto a sheet of controlling electronics. Manufacturers prefer this approach compared to having to build up the pixels themselves within their devices, layer by layer, material by material. Our proof-of-concept breakthrough takes us a step closer to brighter, colour-video e-Paper and the Holy Grail of rollable/foldable displays."

 

 

No pixel borders

Importantly, this paper-thin plastic screen developed at UC is the first among all types of fluidic displays that has no pixel borders.

In current technology, colours maintain their image-forming distinctiveness by means of what are known as "pixel borders." Each individual pixel that helps to comprise the image necessary for text, photographs, video and other content maintains its distinct colour and does not "bleed" over into the next pixel or colour due to a pixel border. In other words, each individual pixel of colour has a border around it (invisible to the eye of the consumer) to maintain its colour distinctiveness.

This matters, because pixel borders are "dead areas" that dull any display of information, whether a display of text or image. Leading electronics companies have been seeking ways to reduce or eliminate pixel borders in order to increase display brightness.

UC's Heikenfeld: "For example, the pixel border in current electrowetting displays, which prevents ink merging, takes up a sizable portion of the pixel. This is now resolved with our electrofluidic film breakthrough. Furthermore, our breakthrough provides extraordinary capability to hide the ink when you don't want to see it, which further cranks up the available brightness and colour of the display when you do want to see it. With a single, new technology, we have simplified manufacturability and improved screen brightness."

 

 

Foldable e-devices as environmental electronics

The first generation of foldable e-devices will be monochrome. Colour will come later. Eventually, in the late 2020s, they will feature magazine-quality colour, be viewable in bright sunlight and run on low power. "Think of this as the green iPad or e-Reader, combining high function and high colour without the weight of a heavy battery, readable out in the sunlight, and foldable into your pocket," says Heikenfeld.

The device will require low power to operate since it will charge via sunlight and ambient room light. It will only use wireless connection ports, and be so durable that you could leave it out overnight in the rain. In fact, you'll be able to wash it or drop it without damaging the thin, highly flexible casing and screen.

This latest proof of concept research verifying the functionality of electrofluidic imaging film builds on previous research out of UC's Novel Devices Laboratory. That previous research broke down a significant barrier to bright electronic displays that don't require a heavy battery to power them.

Most of today's colour-saturated devices – such as LCDs, tablets and smartphones – require high power (and consequently, a larger battery). This is largely because they need a strong internal light source within the device to "backlight" the screen, as well as colour filters in order to display the pixels as colour/moving images. The need for an internal light source within the device also means visibility is poor in bright sunlight.

The new electrofluidic imaging film will require only low-power to produce high speed content and function, because it makes use of ambient light, as opposed to a strong, internal light source within the device.

 

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