Touch Screens

Kiosks have two layers: 

plastic on top and glass underneath, which are spread with conductive material, meaning they conduct electricity together.

How does it know where it's been touched?

A grid sends electricity to the processor under where it's touched.

However kiosks require a lot of pressure from fingers to be used it, but restaurants use them as it is more durable.

Phone screens have four layers:

1. The SiO2 glass is the first layer, only serving as a protective shield.

2. The Conductive Coating is made of indium tin oxide (ITO), a compound commonly used for this. It carries electrical charges across the screen. Upon closer, electrons are immobilized by an insulator, creating a negative electric field and the top layer to store positive charges, a capacitor. 

As a result, if something conducting electricity (finger) touches it, it messes up the electric field and changes the amount of positive charge on the top layer. 

When the finger touches, the amount of electrons are calculated by the processor underneath.

3. Beneath is an insulating preventing electrical current from flowing between the previous layer and the device.

4. Below is a second layer of transparent conductive material, a grid or matrix of electrodes.