How Things Work: Touchscreen technology comes in different forms

In a world in which we rely so much on our touchscreen devices, it’s hard to imagine that such technology did not exist until a few decades ago. But, in fact, touchscreen technology had a long history before it became that smartphone in your pocket.

Historians believe that touchscreen technology first emerged in the 1960s. At the Royal Radar Establishment in Malvern, U.K., E.A. Johnson introduced capacitive touch. A decade later, American inventor Dr. G. Samuel Hurst developed the resistive touchscreen while conducting atomic physics research at the University of Kentucky.

Later, in the 1980s, a number of researchers were involved in the development of multitouch technology, including Nimish Mehta, Myron Krueger, and Bob Boie. At the same time, touchscreens were beginning to be heavily commercialized. In September 1983, the Hewlett-Packard Company (HP) introduced the HP-150, which was a computer that used infrared (IR) emitters and detectors to sense the user’s touch. However, not only was HP-150 costly, but it also possessed some usability issues.

Then came the 1990s, when touchscreen technology was applied to smaller devices in the form of cellular phones and personal digital assistants (PDAs). The Palm Pilot PDA found the most success during the era, especially in the business world. However, it wasn’t until the 2000s that the advancement of touchscreen technology began to elevate dramatically. The world was in for a shock when, in a 2007 Apple press conference, Steve Jobs demonstrated the slide-to-unlock and swipe-to-scroll hand gestures on the first iPhone. The rest is history.

But how exactly does a touchscreen work? In truth, there is no straightforward answer, as touchscreens come in multiple variations. Here, we will explore the basics of a few existing touch technology systems.

As mentioned earlier, capacitive touch was the first touch technology to be developed. In a capacitive device, the capacitive system is located on a glass panel of a monitor, which consists of inner and outer metallic glass layers that conduct electricity. Sandwiched between the layers is an insulator. When you bring your finger toward the screen, you take in some of the charge from the capacitive layer. The decrease in charge of the capacitive layer is quantified by circuits situated at the corners of the monitor, allowing a computer to determine exactly where you touched the monitor. The computer then sends the calculated location to touchscreen driver software. In contrast to capacitive touch, resistive touch transmits less light from the monitor, providing a less clear picture. Nevertheless, resistive touchscreens are inexpensive to produce, making them the most popular design used. They have the ability to recognize multi-touch input, which has given rise to many of our current touchscreen devices.

Similar to the capacitive system, the resistive system is made of two layers with an insulator. However, in a resistive system, the upper layer is composed of a flexible and conductive, polyester plastic. As you press your finger on a resistive screen, you bring the polyester into contact with the glass, which creates a circuit. In comparison to the capacitive system, the resistive system is more accurate in calculating the coordinate location of your touch as it takes note of the change in the electric field.
There are also touchscreen technologies that can sense your fingers through sound. In a surface acoustic wave (SAW) system, the glass plate of a monitor contains transmitting and receiving transducers, as well as reflectors, that are positioned along the perimeter of the screen. Ultrasonic sound waves are reflected from one transducer to the other. However, when you touch the screen, you disrupt the flow of sound beams, while also absorbing their energy. The location of the touch can then be recorded by the receiving transducer. Possessing no metallic layers, the system has excellent light transmission, making it ideal for displaying high quality graphics.

As touch systems continue to advance, the consumer world continues to demand more current technology. At the same time, the explosive growth in technology within the past decade foretells a future of endless possibilities. But as we continue to tap or swipe our phones or tablets, we should not lose sight of the extraordinary human collaboration that went into creating the touchscreens that, decades ago, could only be found in science fiction and movies.