Capacitive touchscreen technology is all around us. Even if you’re unfamiliar with the technology, you’ve probably used a capacitive touchscreen before. From smartphones and tablet computers to smart appliances, human machine interfaces (HMIs) and more, countless touchscreens are powered by capacitive touch-sensing technology. To create these devices, manufacturers must use certain types of materials.
What Is a Capacitive Touchscreen?
A capacitive touchscreen is a type of touchscreen device that identifies touch commands using capacitance. Unlike resistive touchscreens, capacitive touchscreens don’t rely on pressure to identify when and where a user touches the display interface. Instead, they measure capacitance while looking for a reduction of a uniform electrostatic charge.
If you tap or touch the display interface of a capacitive touchscreen with a bare finger, your finger will absorb some of its uniform electrostatic charge. When this occurs, the device’s capacitance will drop. The capacitive touchscreen will then recognize this reduction as a touch command.
You can’t use just any object to perform a touch command on a capacitive touchscreen. Unless the object is electrically conductive, it won’t absorb the device’s electrostatic field. And if doesn’t absorb the electrostatic field, the device’s capacitance will remain uncharged, meaning it won’t register your touch command.
Most styluses, for example, don’t work with capacitive touchscreens. Rather, they only work with resistive touchscreens. This is because styluses are typically made of plastic, which isn’t electrically conductive.
The Materials Used in Capacitive Touchscreens
Although there are exceptions, most capacitive touchscreens feature a display interface made of an insulator material, such as glass, that’s coated in a layer of indium tin oxide (ITO). This is important because ITO is an electrically conductive material. Therefore, touching it allows your finger to absorb some of the capacitive touchscreen’s electrostatic field, resulting in a decrease in capacitance that’s used to determine the location of your touch command.
Projected capacitance touchscreens use a similar design but with one major difference. On the conductive layer, capacitive touchscreens have a grid of horizontal and vertical electrodes. Because they contain a grid of electrodes, projected capacitance touchscreens offer a higher resolution as well as increased input accuracy.
The display interface of a capacitive touchscreen is made of ITO-coated glass. The presence of the ITO allows them to identify touch commands by measuring capacitance. When any conductive object, including a bare finger, touches the display interface, it will absorb some of the device’s electrostatic field through the ITO.