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How do touchscreens work?


touchscreen1One of the driving forces behind science fiction is predicting technology of the future. Certain propositions like human teleportation and warp drive (traveling at speeds faster than light) have been deemed scientifically impossible, but others have been eerily accurate. One of the clearest examples of this is how touchscreen devices now not only exist, but are commonplace. Touchscreen technology was first developed for specialized research products in the 1970s, but now they are found in everyday devices, including cell phones, computer screens, and GPSs.


Touchscreens were never considered impossible, but when the idea of them was first conjured up, no one could have predicted how omnipresent they would become. They first started gaining momentum with the introduction of PDAs and certain handheld video game consoles, but it wasn’t until the iPhone was released in 2007 that touchscreens began to be used in nearly every new technology, revolutionizing the electronics market. What, then, was different about the iPhone that made it such a catalyst for future touchscreen technologies?


Touchscreen technology prior to the iPhone used the “resistive” method. The idea behind the “resistive” method is quite simple: two thin layers, usually made of tough plastic, are spaced a miniscule distance apart with electricity running in between. The screen is above the upper layer and the LCD display is below the bottom layer. When the screen is pressed, it forces the top layer against the bottom layer so sensors can detect where the two meet. One of the best conveniences of this method is that it can detect touch from anything that presses down on the layers, whether it is a finger or a pen cap. However, this method can only recognize one point of contact because only one point can be fully depressed at a time and as a result, does not have smooth sliding and dragging motions (“Touchscreens”). Although this method is now considered largely outdated due to the mass market of iPhone technologies, it is still used on some ATMs and in-car screens.

touchscreen2On the other hand, iPhones, iPads, Samsung Galaxy smartphones, and Amazon’s Kindle Fire, to name a few, use the “capacitive” method. These electronic devices monitor changes in electrical currents running through the screens. The touchscreens include a layer of capacitive, or electricity-storing, material. The capacitors in the screen are arranged according to a coordinate system, creating a grid. The circuitry inside the screen can then sense changes in electrical charge at each point along the grid. As a result, every individual point on the grid generates its own signal when touched, which is then relayed back to the device’s processor, allowing the device to recognize multiple points of contact.

The downside to using this method as opposed to the resistive method is that capacitive screens function by sensing the electrical charges on your skin that are produced when your finger interacts with the electrical field. And so, a capacitive screen won’t work if the user is wearing gloves or if a stylus is being used (Wilson). Nonetheless, the capacitive method is much more responsive and versatile than the resistive method.


This technology has evolved from phones to tablets to computers in the span of about five years and is still continuing to expand. One company has created a projector that can turn any surface into a touch screen, such as a desk, a wall, or even a human hand. Another company has developed a way to manipulate the electrical force between your finger and the screen to create textures on the glass. If touchscreen technology continues to develop further, it can be used in an infinite number of incredible ways, continuing on the path of transforming science fiction into scientific fact.

 Written by Constance Kaita

Works Referenced

Images courtesy of and

“Touchscreens: How they work.” The Washington Post. 23 January 2012. Web. 28 June 2013.

Wilson, Tracy V. and Wesley Fenlon. “How the iPhone Works.” 20 June 2007. Web. 28 June 2013.

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