Touch screen technology can seem very advanced and actually rather complicated yet the concept is quite simple. Without breaking down the LCD screen itself, there are four main layers in a touch screen; the LCD screen, a rigid substrate, a spacer and then plastic film.
So when you push down on the film, it makes contact with the glass and completes the circuit. This is because the glass and the plastic film is covered with a grid of electrical conductors, and the fine metal wires create a grid on the screen. The touch position is then calculated based on the amount of resistance at the point of contact, and that’s all there really is to it.
Most smartphones today include LCD touch screens, and the manufacturing process is actually simpler than some might think, but at least now you know what’s happening when you touch the screen on your device.