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our cell phone will soon be as thin and flexible as a piece of paper.

Cell-phone technology has been increasing rapidly, including screen technology. Most cell phones we see today use touch screens and, although we like to have a big screen, we do not like to carry big and thick screens around with us.

In February 2008, Nokia first released a product to the press called the Morph as a possible future of cell phones using a flexible display. Three years later, Nokia once again showed its interest in the flexible
display with the release of the Kenetic prototype in London.

In January 2013, Samsung announced their future smartphone with a flexible organic light-emitting diode (OLED) display, called YOUM. After years of research, they have finally created the prototype of a plastic-based OLED display, replacing the glass-based OLED display, to make it flexible.

In October 2013, LG announced its prototype, the LG G Flex, also a smartphone with a flexible OLED display. The LG G Flex is planned for release onto the market this year. However, according to the LG website, the flexibility of this curved smartphone is limited. It may be bent flat up to 180 degrees, but only for a limited period of time.

So, what are these OLED displays that are the future for ultra-thin, flexible cell phones?

OLED is made from carbon and hydrogen; it emits light when an electrical current is applied. It is thin, about 200 times more thin than a human hair, and transparent. The components of an OLED display comprise substrate, electrodes and organic light-emitting layers.

The substrate is made up of plastic, glass or foil to support the OLED. Electrodes comprise anodes (positively charged electrode, an electron receptor) and cathodes (negatively charged electrode, an electron donor), through which the electrical current is passed. The organic light-emitting layers consist of a conductive layer and an emissive layer, where the light is made; both elements are made of organic plastic molecules.

Recently, researchers have been studying an alternative material to replace indium tin oxide (ITO), the traditional electrode used in OLED technology. This new material, graphene, was discovered in 2004.

ITO is normally used in powder form and yellow-green in color, but as a thin film form (around 100-300 nanometers thick), it is colorless and transparent. However, due to its scarcity, ITO is expensive and, more than that, it is hard to recycle.

Graphene is made of carbon, is inexpensive and can be found easily. It is also completely transparent, strong, flexible and very thin '€” thinner than the ITO thin film. Moreover, it has extreme conductivity, which is why it is a promising candidate to replace ITO electrodes in the near future.

This magic material is also tougher than a diamond, 200 times stronger than steel and, yet, it is flexible. This is why cell phones in the future may not just be flexible but also foldable, like a piece of
paper, and unbreakable '€” even if you step on it.

Researchers in South Korea, in collaboration with Samsung, have constructed a 30-inch, foldable, graphene, touch-sensitive screen. It is a promising step toward future graphene-based displays, and it may soon be used for screens on cell phone.

However, there is still one challenge remaining in the quest to build a completely foldable, ultra-thin cell phone. It is not just the screen that needs to be foldable, but all the components inside it as well, including the battery and processor.

Phones will still need a battery to remain mobile. That is why the prototype still has a relatively thick section as well as its thin screen, for the attachment of other of the phone'€™s components.

A graphene battery has been proposed, which would be a super-capacitor that can hold a great amount of power and be charged within just a few seconds. This means that one day, we may have ultra-thin, flexible batteries that can be used with any device. However, producing graphene-based displays and graphene batteries is still a major challenge. Although the material can be easily sourced, the process of producing large amounts of graphene is not so simple.

Whatever the current challenges, however, we need to reflect on the rapid advances in technology that have seen cell phones progress from the original, thick and heavy phone, which was introduced in 1973 by Martin Cooper, to the era of touch-screen smartphones. Thus, the foldable and ultra-thin cell phone era is probably just a matter of time.