Unbeknownst to most users, capacitive touchscreens feature indium tin oxide (ITO) in their construction. Capacitive touchscreens leverage capacitance to detect touch commands. During use, they’ll produce a uniform electrostatic field across the display interface, which they’ll constantly measure. Any changes in this electrostatic field will signal a touch command.
There are different types of capacitive touchscreens. Some of the most common include surface capacitive, mutual capacitive and self-capacitance. Regardless, they all require a conductive layer. For this conductive layer, ITO is typically used.
What Is ITO?
ITO is a mixture of the materials after which it’s named. It consists of indium, tin and oxygen. While the exact ratio of these materials may vary, most ITO formulas contain around 74% indium, 18% tin and 8% oxygen.
How ITO Is Used in Capacitive Touchscreens
Most capacitive touchscreens feature a layer of ITO. It’s typically found on top of the overlay. The overlay, of course, is a sheet of glass. During production, manufacturers will coat the overlay with ITO.
Why Capacitive Touchscreens Feature an ITO Coating
Capacitive touchscreens feature an ITO coating so that they can detect touch commands. On most capacitive touchscreens, the top of the overlay features an ITO coating. A voltage is then applied to the bottom of this same overlay. ITO is conductive, so the voltage will travel through the overlay while creating a conductive touchscreen interface.
If you touch the overlay with a bare finger, the capacitance will change. All capacitive touchscreens work by measuring changes in capacitance. A voltage will travel through the overlay, and if you touch or tap the interface with a conductive object — such as a bare finger — the capacitance will change. An ITO coating facilitates this operation by allowing the voltage to travel through the overlay.
The overlay is typically made of glass. Glass, of course, isn’t conductive. Even if a capacitive touchscreen applied a voltage to the bottom of a glass overlay, it wouldn’t be able to sense changes in capacitance. ITO offers a solution. When coated in ITO, electricity can travel through the overlay. You can touch the overlay, at which point the capacitance will change.
The Bottom Line
The capacitive touchscreen will then register your touch command. Capacitive touchscreens feature an ITO coating to sense touch commands. ITO is a mixture of indium, tin and oxygen. It’s applied to the overlay of capacitive touchscreens as a transparent and conductive layer.