How do touch screens work?

August 10, 2021

Magic.

Well, almost. It's actually clever technology and amazing engineering. There are several types of touch screen technology in the market, and with the advent of mobile telephony, the most common is capacitive screens. Capacitive screens allow us to interact with the devices without the use of keyboards or mice, which has revolutionized user interfaces.

Capacitive screens have been in development since the ‘60s, but they were massively popularized with the introduction of Apple’s iPhone. The first iPhone launched in 2007 featured a screen of 3.5” measured diagonally and a resolution of 320x480 pixels. An estimated 6.1 million units were sold over the course of 13 months. Since then, hundreds of millions of devices with capacitive screens have been sold throughout the world.

Capacitive screens work by generating a very small current across a grid placed just below the surface of the screen. When the current is disturbed by a conductor of electricity, the device locates the position using hardware and software, and thus interpreting an input. Human bodies are conductors of electricity, so by touching the capacitive screen with our bare fingers, we are effectively disrupting the electrical field and allowing the device to interpret our touch. Don’t worry, the current flow is so low that we don’t feel anything.

Capacitive screens are not only incredibly accurate and fast at understanding our intentions, but they also allow the displays to produce high resolution content with a nearly unlimited color gamut and high contrast ratios.

It seems as though there are no downsides to capacitive touchscreens. However, whenever an insulator is introduced between the screen and our skin, the flow of energy is interrupted and nothing happens. Such is the behavior when we touch a capacitive screen while wearing gloves. Nothing happens! Fortunately, it is possible to recreate our conductivity and provide the device electrical signal an escape path and therefore recreate touch. All that is needed is a conductive material on the outside of the glove. Read our entry on how touch screen gloves work to find out more.