대학신문방송국

Flexible Phones?

By Yoo Jay  Reporter, Senior of Material Science and Engineering

Now, we are living in an age of innovation. In 2007, a man wearing jeans and a black turtleneck took a small device out of his pocket. Then he completely changed the concept of cell phones. We can text a message, make a phone call, send an email, and use IT technologies, just by touching the phone screen. Thanks to this convenience, smartphones have become a part of our daily life. According to the Gallup Korea poll, conducted in 2021, the percentage of Korean adult smartphone users is currently 95 percent. In addition, according to data from the Korea National Statistical Office in 2021, adults use smartphones on average for four hours a day. Now, we feel that smartphones are like an essential part of our body. So, why don’t we know what will happen on the mobile phone, which is just like a part of our body?

Since people do most activities using a cell phone, there is one essential thing that mobile phones must have. It is portability. The latest smartphones are portable, but engineers are studying these items to increase their portability. How comfortable would it be to fold your cell phone like paper and put it in your pocket? In fact, many engineers are researching a variety of FormFactors (FormFactor : the physical shape of things and their appearance) that can be folded, and rolled. The display that can transform its form factor is called a flexible display, and many experts say that this technology is going to bring the next innovation to future cell phones. Surprisingly, some products have already been developed and are on the market. Let’s figure out about cell phones according to the flexible stages.

Stage 1 Flexible Display:  Durable Display

Durable Display phones have a curved screen as a whole. Since flexibility is required to bend the display, the substrate should be made from an elastic plastic, instead of the existing unbending glass. This technology was applied to ‘G Flex’ that was launched from LG Electronics. This product fits our usage more comfortably. That means that the speakers and microphones can be positioned as close as possible to the ears and mouth. It can help users to hear better, and also increases the clarity of their voice for the  listener.

Stage 2 Flexible Display: Foldable·Rollable Display

Rollable display is a flexible display that allows cell phones to be rolled up like toilet paper. In contrast, a foldable display is a flexible display that can be folded. A radius of curvature of the substrate around 10mm is required for a stage 1 flexible display. For stage 2, it needs a considerable decrease in the radius of the curvature of the substrate. So, it is essential to the macromoleculization of the substrate. This technology was applied to the ‘Galaxy Z Flip’  that was launched from Samsung Electronics in 2020. We can fold this product and put it in our pocket. You can enjoy a large 6.7inch / 17cm screen by spreading the display. Also, it can be spread out at various angles, so we can freely use our hands to do other things during the video call.

Stage 3 Flexible Display: Stretchable display

The ultimate goal of the flexible display is a stretchable display. It can be bent, folded, or stretched in the desired directions. After removing the stretching force, it returns to its original material’s shape. For this technology, it is essential that the substrate, electrodes, and shields have a high restoration force. Once this technology is developed, we will be able to put our cell phones in our pockets like paper, and go to school. Then, take them out of our pockets for team projects, spread them out on large screens, and use them together. 

It is not the amazing thing that cell phones are folded anymore. Just 10 years ago, the foldable phone was a fantasy product in SF movies. However, how is it now? You can often see advertisements for ‘Z flip,’ a flexible product, while passing through the street. The Stretchable displays, which are the last stage of flexible displays, have not yet been developed, but many research results continue to come out. Soon, stretchable displays that stretch like rubber bands will no longer be a surprise.