How Do Touchscreens Work?

How do Touchscreens work? What enabled smartphones to dominate as a technology- to be so prolific and critical to our lives that I I would rather lose my car keys or wallet than my smartphone. The answer to this question isn’t a simple one liner, but rather it's a combination of answers, app development, wireless internet, carrier networks, Steve Jobs’ brilliant marketing, tho I would argue the most important contributor was the seamless combination of different functions and technologies into a single package. In this episode we're going to explore the most distinctive feature of the smartphone’s merging of technologies- the touchscreen display.

There are three technologies within the touchscreen display These technologies are combined all on top of every other. When you felt and used a smartphone for the first time, you just knew that you were holding something revolutionary – something different from all previous phones. These… were not new technologies. Many devices used a tactile interface, and color displays had already been a typical for many phones. Even toughened glass had been discovered in the 1800 s. 

But the innovative element was combining them seamlessly. One layer on top of another like magic. Ok, so let’s get into the layers of a touchscreen display. On the top, we have the protective glass. A lot of us have had a screen shatter but think about how many times you’ve dropped it and it hasn’t. That’s because a smartphone’s glass is over 5x stronger than normal glass. And, before the first iPhone showed up in 2007 the standard for cellphone screens was plastic and although plastic doesn’t shatter, it is very easily scratched. If the screen were covered in plastic, it wouldn’t last a week sitting in your pocket next to your keys before having dozens of scratches all over it. 

Each sub pixel's candlepower is controlled by a little thin film transistor that acts as a dimmer switch. There are many layered structures in each sub pixel, however explaining the function of each layer will have to be saved for a future episode. Photons are produced in the sub pixel by electrons that are driven from the negative to the positive terminal. When they pass through this middle layer here, called the missive layer,photons are emitted through a release of energy. The compounds used to make up the missive layer determines the color of the light emitted, and the intensity of this light is dependent on how many electrons pass through. 

In fact the 2014 Nobel prize in Physics was awarded to 3 researchers for their discovery of efficient blue light emitting diodes! So, let’s summarize: on the bottom is an OLED display composed of a 10 million itty bitty little colored lights. On top of that is a transparent projected capacitive touchscreen that can sense one or multiple finger touches at a time. And on top of that is strengthened glass that protects your screen from scratches and most falls. Now you too are a touchscreen expert! If you have any questions, post them to the comments below. Subscribe, Like, and tell your friends or family about something you learned. This episode details the structure of a touchscreen display. 

Branches from this episode are: Multi touch design, electric fields, Capacitors OLEDs and their control, LCDs, Why are materials transparent? And interface aesthetics. Thanks again for watching and until next time, consider the conceptual simplicity yet structural complexity in the world around us.