How does a touchscreen display works?

How do smartphone/iPad/tablet touchscreens work?

The anatomy of a smartphone touch screen consists of many layers the first layer being a protective insulating glass usually chemically toughened glass on top and the lowest layer consists of the display panel technology that is either LCD (Liquid Crystal Display) or OLED (Organic Light Emitting Diode) that produces the image you see and between the top and the lowest layer there are other several layers that forms a working smartphone touchscreen.

Before the use of toughened glass it used to be plastic on top of the displays during the early days, however, due to its scratch-receptive nature, manufacturers had to go with toughened glass. What makes these toughed smartphone glass so tough is that they are soaked in potassium nitrate to make them tough.

There are a lot of touchscreen technologies in use, but the most common touchscreen technology used today on smart devices that common people use are resistive and capacitive touchscreen technology. Below the toughened glass there is a resistive or capacitive touchscreen technology that is used to detect the touch of fingers.

Resistive touchscreen technology is often seen in ATM machines, card payment machines etc. This technology works by pressing the screen hard enough that the screen makes a bend and resist the touch. Basically, it has two layers and an electrical current runs between these layers, the top layer is the conductive layer usually made with plastic and the lowest layer is resistive usually made with glass, when a user presses the screen hard enough the top layer will get pushed down to the lower resistive layer creating an electric circuit making a change in the current in that particular section of the screen/ display, this change in the current will be detected by the OS in the computer and makes the magic happen by responding to users touch. Resistive touch screens are reliable and durable which is why they are found in most of the public used machines/ computers like ATM machines etc.

However, these screens do not provide a clear view of the screen making it difficult for users to read when light hits the screen due to its multiple layers. This is why it is harder for users to see the display in most ATMs that are placed outside due to the sunlight hitting the screen. This is what makes the resistive display technology so different from the capacitive touch display technology used in most of the smart devices today along with some other differences like the lack of a zoom-in feature and the lack of multi-touch in the resistive display which is otherwise present in the capacitive display.

A Capacitive touchscreen display technology works in a different way. This touchscreen made up of various nodes that act as capacitors storing electrical charge. These screens usually work by altering the current under the display when touched by anything that holds an electrical charge such as the fingertips of people because the human body contains atoms that are negatively and positively charged and this contributes to altering or changing the current under the capacitive display. The moment you touch a capacitive touchscreen a voltage drop occurs on the particular place on the screen because an electrical circuit takes place and the software or OS detects this voltage drop and detects it as a touch. This is the main reason why the touch screen won't works when used with hand gloves since most of them act as insulators don’t conduct electricity to pass through. There are two different kinds of capacitive touchscreens, projective display and surface display and these displays are made either from Indium tin oxide or copper oxide which keeps electrical charges in nano strips thinner than a hair strand.