When you think about touchscreens today, you probably think about smartphones and tablets, and for good reason. The 2007 introduction of the iPhone kicked off a transformation that turned a couple of niche products—smartphones and tablets—into billion-dollar industries. The current fierce competition from software like Android and Windows Phone (as well as hardware makers like Samsung and a host of others) means that new products are being introduced at a frantic pace.Welcome back to our three-part series on touchscreen technology. Last time, Florence Ion walked you through the technology's past, from the invention of the first touchscreens in the 1960s all the way up through the mid-2000s. During this period, different versions of the technology appeared in everything from PCs to early cell phones to personal digital assistants like Apple's Newton and the Palm Pilot. But all of these gadgets proved to be little more than a tease, a prelude to the main event. In this second part in our series, we'll be talking about touchscreens in the here-and-now.
The screens themselves are just one of the driving forces that makes these devices possible (and successful). Ever-smaller, ever-faster chips allow a phone to do things only a heavy-duty desktop could do just a decade or so ago, something we've discussed in detail elsewhere. The software that powers these devices is more important, though. Where older tablets and PDAs required a stylus or interaction with a cramped physical keyboard or trackball to use, mobile software has adapted to be better suited to humans' native pointing device—the larger, clumsier, but much more convenientfinger.
The foundation: capacitive multitouch
Most successful touch devices in the last five or so years have had one thing in common: a capacitive touchscreen capable of detecting multiple inputs at once. In this way, interacting with a brand-new phone like Samsung's Galaxy S 4 is the same as interacting with the original 2007-model iPhone. The list of differences between the two is otherwise about as long as your arm, but the two are built upon that same foundation.
We discussed some early capacitive touchscreens in our last piece, but the modern capacitive touchscreen as used in your phone or tablet is a bit different in its construction. It is composed of several layers: on the top, you've got a layer of plastic or glass meant to cover up the rest of the assembly. This layer is normally made out of something thin and scratch-resistant, likeCorning's Gorilla Glass, to help your phone survive a ride in your pocket with your keys and come out unscathed. Underneath this is a capacitive layer that conducts a very small amount of electricity, which is layered on top of another, thinner layer of glass. Underneath all of this is the LCD panel itself. When your finger, a natural electrical conductor, touches the screen, it interferes with the capacitive layer's electrical field. That data is passed to a controller chip that registers the location (and, often, pressure) of the touch and tells the operating system to respond accordingly.
This arrangement by itself can only accurately detect one touch point at a time—try to touch the screen in two different locations and the controller will interpret the location of the touch incorrectly or not at all. To register multiple distinct touch points, the capacitive layer needs to include two separate layers—one using "transmitter" electrodes and one using "receiver" electrodes. These lines of electrodes run perpendicular to each other and form a grid over the device's screen. When your finger touches the screen, it interferes with the electric signal between the transmitter and receiver electrodes.
Because of the grid arrangement, the controller can accurately place more than one touch input at once—most phones and tablets today support between two and ten simultaneous points of contact at a time. The multitouch surfaces of the screens allow for more complex gestures like pinching to zoom or rotating an image. Navigating through a mobile operating system is something we take for granted now, but it isn't possible without the screen's ability to recognize multiple simultaneous touches.
These basic building blocks are still at the foundation of smartphones, tablets, and touch-enabled PCs now, but the technology has evolved and improved steadily since the first modern smartphones were introduced. Special screen coatings, sometimes called "oleophobic" (or, literally, afraid of oil), have been added to the top glass layer to help screens resist fingerprints and smudges. These even make the smudges that do blight your screen a bit easier to wipe off. Corning has released two new updates to its original Gorilla Glass concept that have made the glass layer thinner while increasing its scratch-resistance. Finally, "in-cell" technology has embedded the capacitive touch layer in the LCD itself, further reducing the overall thickness and complexity of the screens.
None of these changes have been as fundamentally important as the original multipoint capacitive touchscreen, but they've enabled thinner, lighter phones with more room for batteries and other internal components.
Let your fingers do the walking: Designing software for the human hand
The touchscreens themselves are important, but the software that powers today's phones and tablets is even more vital. Modern phone and tablet operating systems are made for touch first, and they're designed differently from software made to be used with a keyboard, mouse, or even a stylus.
Let's step back to 2001 or so, when Microsoft first introduced its concept of the "Tablet PC." These early tablets ran a version of Windows XP Professional called the "Tablet PC Edition." It supported pen input and came with a small suite of applications for handwritten notes and other pen-centric tasks.
Despite these additions, the Tablet PC Edition of Windows XP was very much Windows XP with a few new pieces laid on top of it. The pens could be acceptable pointing devices (subject to the quality and accuracy of the touchscreen), but the vast majority of the operating system and the applications that ran on it were designed with the far-more-prevalent keyboard and mouse in mind. (Microsoft Office 2013 is a more recent example of software that was designed for a mouse and keyboard first.) This isn't necessarily a bad thing, but it does make it much more difficult to use with a touchscreen.
Modern operating systems with a touch-first approach are more finger-friendly in two important ways: responsiveness and size.
When we say "responsiveness," we're not only talking about an operating system that responds quickly and accurately to input, though that's certainly very important. When you touch something in the real world, it reacts to your touch immediately, and the operating systems that feel the best to use are the ones that act the same way. Windows Phone makes a point of running smoothly even on low-end hardware, to make sure that its phones feel satisfying whether they cost $200 or were free with a contract. But consistency is also an important element of responsiveness. Android's "Jelly Bean" update included "Project Butter," which focused on making the operating system run at 60 frames-per-second as often as possible. This was intended to improve the sometimes-inconsistent performance of older Android versions.
Another important element here are the little nuances that make using a touch-and-gesture-based operating system feel more natural: this means scrolling that speeds up, slows down, and gains momentum based on how you're touching the screen. When you can't scroll anymore, the OS will usually move and snap back into place to let you know that you can't scroll further (commonly called "rubber-banding"). These behaviors let the user know that their input was recognized, even if that input didn't actually do anything—if yesterday's PCs used blinking lights to demonstrate that they were working, today's touch devices use slick transitions and animations.
The size of onscreen elements is also crucial to a good touch experience—fingers aren't precise enough to easily deal with a bunch of nested menus, checkboxes, and buttons like Windows or OS X use. Instead, you often have to sacrifice information density in favor of making your UI larger. Most touch operating systems have some general guidelines to follow when developing touch applications, but Apple's are well-defined and simple to explain, so we'll use iOS as an example.
Apple's Human Interface Guidelines for iOS define "the comfortable minimum size of a tappable UI element" as being 44 by 44 "touch points" large. On non-Retina displays like the iPad mini or iPhone 3GS, a "touch point" and a pixel are the same size; on a Retina display like the iPad 4 or iPhone 5, one touch point is one 2×2 square of pixels (since a Retina display has four times as many pixels as a non-Retina display). On a phone, the physical size of one of these tappable elements is about 0.38" (or 9.7mm) large, while on an iPad it's about 0.47" (11.9mm) large. Developers are free to use larger or smaller elements (many of Apple's own buttons are smaller), but these measurements exist to give developers a general idea of how much space you need to prevent accidental button presses, mis-registered touches, and anything else the user didn't intend to do.
Because it's so different from mouse-and-keyboard-driven and stylus-driven software, touch-driven software has also transformed the hardware it runs on. Most smartphones include just a few physical buttons: power, volume, a mute switch, and the home button. Using a touchscreen as the primary input obviated the need for things like a hardware number pad or keyboard, since the screen could dynamically become whatever it needed to be. Software keyboards have become even more context-sensitive over time, adding things like a ".com" button when typing in a URL field.
As this software has matured and people have become more used to it, newer phones and tablets have become even more button-averse. Stock Android switched out its hardware buttons for onscreen software buttons (which, like software keyboards, are context-sensitive and can change based on the application you're running). Windows 8 and Windows RT tablets still retain a Windows button, but they rely on gestures and swipes from the edge of the screen. The BlackBerry Z10 does away with even a home button, relying entirely on gestures for not just OS navigation, but also for waking the phone from sleep.
Look around you—touch is everywhere
The success of touch-driven smartphones and tablets have had two overarching effects: for one, consumers are beginning to expect touch, even in places where it hasn't always been (more than once, I've gone back to my MacBook Air after using a Windows 8 Ultrabook for a few days, only to catch myself trying to touch the screen). On the other side of that coin, hardware manufacturers seeking to capitalize on the success of other touch-driven devices have been experimenting with touchscreens in everything from PCs to watches.
For PCs, Windows 8 has given rise to a new class of convertible laptops that try to serve the needs of both touch users and Windows desktop users. These experiments haven't always worked out, but the best of them—designs like Lenovo's IdeaPad Yoga and Dell's XPS 12—add touch capabilities without diminishing the devices' utility as regular laptops. Sony's PlayStation Vita, its forthcoming PlayStation 4, and Nintendo's Wii U all also use touchscreens as a secondary means of input in addition to the respective consoles' signature controllers. All of these devices show that touch can be added as well as disruptive—it can improve already good devices just as readily as it replaced the ungainly smartphones and tablets of the early-to-mid 2000s.
Other experiments on the PC side of the fence attempt to define completely new products. PCs likeSony's Tap 20, Lenovo's IdeaCentre Horizon 27, and Asus' Transformer AiO all combine a traditional all-in-one PC with a large touchscreen that multiple people can gather around at once. This seems especially conducive to entertainment and education—multiplayer games and collaborative exercises are commonly touted as selling points for these big new screens.
Touch seems equally likely to move down into smaller screens. More than one company is rumored to be working on a "smart watch" to augment (or even replace select functions of) your smartphone. It's a fair bet that if these products come to pass, more than one of them will work touchscreens in somehow (though as the Pebble watch shows, they can also work reasonably well without touch). If you owned one of the small, square sixth-generation iPod Nanos, you may have already gotten a glimpse into this future. These devices had touchscreens, a limited selection of apps, and were easy to wear around your wrist in place of a watch, provided you had the right strap.
Touch really is working its way into just about everything with a screen, whether it's enabling brand-new experiences or just augmenting old ones. And that's the present of touch technology: it's successful, it's widespread to the point of near-ubiquity, and it continues to change what we expect from our devices. In our next article, the third and last in the series, we'll be looking precisely at those expectations as we dive further into the future. We'll explore how new technological advancements will continue to shape tomorrow's touch devices, and we'll look at how software will continue evolving to support this new hardware.