Above: Businesswoman touching smartphone (©iStockphoto.com/hocus-focus)
Fast Fact: The first description of a capacitive touch screen (the kind used in the iPhone) was made by E.A. Johnson in 1965. At that time, computers were so large that they often took up entire floors of buildings.Apple is largely credited with revolutionizing the mobile phone industry in 2007, with the release of the first iPhone and its elegantly intuitive touch screen. But touch screen technology isn’t anything new. In fact, the idea was first published in 1965, well before the widespread availability of either cell phones or personal computers.
The same principles are followed in all touch screens. A touch is registered and a computer processes it into a form usable by the device's operating system. But just as there are many ways to store the same information (hard drives, flash drives, RAM, optical disks, floppy disks), there are also many ways to convert a touch into a specific response. Two methods in particular have proven to be quite effective: resistive and capacitive touch screens.
A resistive touch screen consists of two transparent and electrically resistive layers separated by a very thin space. Electric current is then passed through the screen. When the screen is pressed, the layers make contact, completing an electrical circuit. Anything can be used to touch the screen, so long as the screen is physically pressed. However, pressing too hard may cause screen damage and, eventually, a lack of response.
Fast Fact: The iPhone wasn’t the first Apple device to use a touch screen. The Apple Newton, a personal digital assistant (PDA) featuring handwriting recognition, was released in 1993. Apple also apparently built a prototype touch screen phone in 1983.Many smartphones, including the iPhone, work using a capacitive touch screen. This method relies on the fact that the human body is a conductor. For example, charge can move freely from a carpet to your feet, through to your finger, and then to an object you’re touching, resulting in a “carpet shock.” A capacitive screen is composed of a pane of glass covered with a transparent capacitor (a layer that stores charge). Touching the surface transfers charge from the screen to your finger. This loss of charge is sensed by electrodes, which relay a signal to the computer processor.
The iPhone uses a grid of capacitors to assign unique coordinates to your touch. While you don’t have to actually press the screen to get a response from the device (you just need to touch it), the system will only respond to your skin. This can be a problem for those who live in colder climates and regularly wear gloves, which not only keep you warm but also act as electrical insulators.
What is the future of touch screens? It will likely involve solving many of the problems associated with today’s devices. Have you ever touched your smartphone and wondered if it has recognized your touch? It's a problem you rarely encounter on a keyboard. Well, a company call Tactus is currently designing touch screens with “physical buttons that rise up from the surface and then recede back into the screen,” just like on a keyboard!
Fast Fact: IBM released the first smartphone with a touch screen, called the Simon Personal Communicator, in 1994. But it was the PalmPilot, a PDA first released in 1997 (a decade before the iPhone), that really brought touch screens into mainstream use.The second issue with the current generation of touch screens has to do with the limitations posed by the screen itself. Wouldn’t it be nice if almost any surface could serve as a screen? For example, you could simply look at your wrist for the time. Or glance at your bus pass for up-to-minute schedule information. SixthSense is a technology being developed by Pranav Mistry which could make these dreams a reality. Mistry discusses his research in a very cool TEDtalk, which is available online.
But don’t get too excited, because all of this new technology is still in its infancy. Remember, it took over 40 years of development before touch screens could be cheaply manufactured and reliably incorporated into the smartphones we use today!
Touchscreen lowdown – Capacitive vs Resistive (Know Your Cell)
http://www.knowyourcell.com/features/687370/touchscreen_lowdown_capacitive_vs_resistive.html How the iPhone Works (Tracy V. Wilson and Wesley Fenlon, Howstuffworks)
http://electronics.howstuffworks.com/iphone.htm Tactus Technology
Johnson, E.A. 1965. Touch Display - A novel input/output device for computers. Electronics Letters 1:219–220.