Question: How do touch screens work?

Stuart Archer answered on 18 Jun 2013:

There are two main types of touchscreen that you’ll see on phones and tablets that are around at the moment.

1) Resistive touchscreen – these are made up of two thin sheets of glass both of which have a special coating on them. W On each sheet there are lines that can conduct electricity – one has lines going left to right, the other top to bottom. hen you poke the touchscreen, the two sheets are pressed together, and the electrical current that flows through the horizontal and veritical lines can be used to work out register the exact place you touch the screen. You can use this touchscreens with virtually any object – be it a finger, or a stylus (or a French fry as one of my friends once did..). Examples of things you might come across with this type of screen are things like the Nintendo DS and older touchscreen phones.

2) Capacative – These are a little more complicated. Basically, they’re made of a sheet of a material that doesn’t conduct electricity (such as glass) coated on top with another material that does. The most common coating is something called Indium-Tin-Oxide, which is see-through like glass but also conducts electricity. When you put electricity through the conducting material, it forms an ‘electric field’ on the surface of the screen – similar to the invisible field around a magnet. Your finger also is a good conductor of electricit, so when you poke at the screen, your finger changes the shape of the electric field on the surface. This is picked up by other electronics attached to the screen that can work out exactly where your finger is. These are much more sensitive than the resistive screens, but you can only poke them with other things that conduct electricity.