How Do Touchscreens Work?

How many of you know the element with atomic number 49? Hint: you might even be looking at it now. Time’s up! The answer is indium, a silvery metal produced as a by-product of zinc smelting. Most modern touchscreens are made using an indium tin oxide, a mix of indium oxide and tin oxide in a roughly 9:1 ratio. A thin coating of the material is applied to a film (rendering it transparent) and placed on top of LCD panels. When a conductive material like your finger touches the film it disrupts the electrostatic field of the panel, which can be measured and used to calculate the location of the touch. A less precise but more durable type of touchscreen uses two thin films separated by a slight gap. Direct pressure causes the two films to make contact and the resulting voltage change can calculate the location of the input. This type of technology is used more in outdoor applications like ATM screens. Touchscreens were first introduced in the 1960s but really didn’t take off until the early 2000s as smartphone adoption skyrocketed. China is currently the leading producer of indium, followed by South Korea, Japan, and Canada (who claims title to the largest single source, a mine in British Columbia just north of the US border). This article from HP has a great summary of the major types of touchscreen technologies and a history of their use.