How a touch screen works?

We all use a smart phone almost every single day, most of them are touch screens. Ever wonder how a touch screen of a smart device works? Before the legend and Co-founder of Apple Inc. STEVE JOBS introduced Capacitive touch to the technology world there was something called Resistive touch.

The working of resistive touch was very simple, there were two layers called Resistive layer and Conductive layer, when our finger pushes both layers at ones then the local voltage is changed and it recognises the touch and responds.

On June 29, 2007, Apple Inc. co-founder STEVE JOBS introduced a new touch technology with the first iPhone so called CAPACITIVE TOUCH. As soon as it was introduced rest of the companies started working with capacitive touch.

So, how a capacitive touch works?

Unlike resistive touch screens, capacitive screens do not use the pressure of your finger to create a change in the flow of electricity. Instead, they work with anything that holds an electrical charge – including human skin. Yes we humans do hold electric charge. Capacitive touch screens are constructed from materials like copper or indium tin oxides that store electrical charges in an electrostatic grid of tiny wires, each smaller than a human hair.

There are few layers in it, the first layer is glass, we commonly use gorilla glass. The next two layers are filled with electrodes which are very tiny. One of those contain the Driving lines which carry current and the other one contains the sensing lines which sense the amount of current. These layers are arranged such aa way that the driving lines and the sensing lines are perpendicular to each other. Now when we move our electrically conducting finger on to the screen, it changes the amount of charge. As soon as it changes, the sensing lines sense, where the charge is changed (i.e, jumped) on the driving lines. And the result is shown on the layer( LCD screen).  It also work the same way with multiple touch and the moving the finger on the screen.

This is the reason why we can only work with our touch devices with electrically conducting things like our Finger. So thanks to Steve jobs.