Technical overview about capacitive sensing vs. other touchscreen-related technologies

Not all touch screens are created equal. Ever since the first touch screens came into being as part of an effort to improve the technology of air-traffic control systems, there have been many versions. In 1972, students at the University of Illinois developed an optical touch screen for computers that linked an array of predetermined points in a matrix. A year later, George Samuel Hurst filed for a patent for the first resistive touch screen. Capacitive touch screens, at least in theory, are at least eight years older than either the optical or resistive technologies. E.A. Johnson wrote a paper in 1965 that outlined his theories and body of work on capacitive touch screens.

What are the Differences?

Capacitive touch screens react to the touch of something that has capacitance. In most cases, this is the skin of someone's finger. Otherwise, it's something artificial that mimics the capacitance of human skin, such as a specially designed stylus. Sensors inside the device detect the change in electric charge and react accordingly. Projected capacitance is even more accurate because it forms a triangulated grid around the point of touch. Additionally, the extra accuracy allows for the use of screen protectors or heavy-duty screens, such as Gorilla Glass.

Resistive touch screens don't rely on an electrical reaction. Instead, they use two sheets of circuitry that are separated by air. Each sheet is implanted with sensing electrodes that, when pressed together, provide the location on the screen. Because no capacitance is required, resistive touch screens react to any object used to touch them. Resistive touch screens are less sensitive than capacitive touch screens but are more accurate. They are also more susceptible to damage but are also less expensive to produce, repair or replace.

Optical touch screens have come a very long way since 1972. They don't even require a physical touch anymore. The sensors detect an object that is simply near the screen. Optical touch screens are also useful in large computer monitors and have been used in many machines operating Windows 7 or Windows 8. These touch screens will even operate if the surface is scratched.

Other Innovations

Multi-touch screens were the biggest innovation in the industry. They allowed users to manipulate more than one input at a time. "Pinch to zoom" is the most famous application of multi-touch. Multi-touch screens also allow for gestures to complete preassigned tasks, such as performing a character's specialty moves in a computer game or app.

Convex and concave touch screens were 2014's newest gadgets and were featured on slot machines in Las Vegas. In 2015, several companies are also experimenting with GelTouch, which will use gel to form physical buttons on an otherwise flat touch screen. The gel reacts differently to various levels of electrical current and can form multiple buttons of changing shapes and sizes on the same spot on the screen. Only time will tell what's next in this exciting industry!