How does a touchscreen work?

June 3, 2011

Let’s take a look at the all-powerful iPhone as an example of just how a touchscreen works in practical use.

The iPhone touchscreen is actually made with one of two different types of projected capacitance touchscreen, self capacitance or mutual capacitance. The difference is in the way the electrical change is sensed by the system. Self capacitance touchscreens use a layer of transparent electrodes to hold the charge. A mutual capacitance system has two lays of electrically charging sensor lines that read finger disruptions. In both cases, touching the screen with your finger, which is a conductor, disrupts the electromagnet charge and tells the phone where the energy on the screen has been disrupted.

In a simple scenario, let’s say you want to play Angry Birds on your smartphone. You touch the icon on your screen and the program opens. The phone reviews its database and connects your movements in relation to the programming of the game. When you touch the screen at the location of a bird and slide it back on the catapult, the bird follows, as soon as your finger lifts, it stops disrupting the electric charge. The sensors send a message to the game that it has been interrupted, and the bird is released. Depending on the bird, if you tap anywhere on the screen while it’s in flies, the game responds in a specific way.