Touchscreens are often used with haptic response systems nowadays. We all know that the only way to operate an increasing number of modern devices, from smartphones to cash machines and cars, is the deft use of a finger on a touchscreen, with a tap for this and a swipe for that. But sometimes such actions do not work all that well. It is easy to miss the required key on a tiny virtual keyboard and produce spelling errors. Sometimes the screen fails to respond at all. And it can be downright dangerous to take your eyes off the road to flip through myriad air-conditioning options on a vehicle's control panel. Now help, as it were, is at hand. As touchscreens become ubiquitous on devices, new ways to make and use them are emerging.
Robert Bosch, a German producer of car parts, among other things, recently displayed a touchscreen with "haptic feedback". Visual effects, sounds and vibrations are already used with touchscreens to confirm when icons or keys are selected. What the Bosch system does is to add different surface textures to the mix.
The textures on the screen can be rough, smooth or patterned in various ways to represent the location of different buttons with different uses. The idea is that a driver would be able to feel for the right button without having to look at the screen. To avoid accidentally activating buttons as he feels his way across the screen, the driver needs to press a particular surface more firmly to turn the required function on or off, much like pushing on a mechanical switch. By applying variable pressure, a user can scroll faster or slower through, say, different music tracks or radio stations.
Because neoSense, as Bosch calls the system, is still under development the company will not say how it works other than that it uses a conventional touch sensor coupled with a sensor that measures the amount of pressure from fingers. That gives little away. Bosch is probably doing something similar to other groups working on such systems: placing under the screen a thin device that generates specially tuned vibrations in the area of the virtual buttons. The pattern of these vibrations would create textured effects that could be felt by the user’s fingers as if they were physical elements on the screen.All charged up
Although research into touchscreens dates back to the 1960s, they did not appear on consumer gadgets until the 1980s. Many of these early screens were the "resistive" type, which in its simplest form relies on a finger pushing against a ductile screen to press two underlying conductive sheets together to complete an electric circuit. The point of contact is measured to provide the co-ordinates of the finger.
Resistive screens are cheap to make and tough: lots are still used in restaurants to take orders and in factories to control machines. But many devices, particularly smartphones and tablets, now use a system that relies on capacitance. (Capacitance is a measure of an object's capacity to store an electric charge. The charge builds up if there is no circuit through which the electrons can flow and is dissipated when a circuit is completed—in extreme cases as a jolt when static electricity builds up in the body and is discharged when touching something metallic.)
There are a number of ways in which capacitive touchscreens can be made. The current favourite uses a grid of tiny wires made from a transparent, conducting material, usually indium tin oxide, just below the surface of the screen. When a finger touches the screen, or is very close to it, an electrostatic field created in the grid is disturbed by a small change in capacitance at the point at which the charge transfers to the finger. The software in a chip which controls the screen detects the position of the change in capacitance and uses it to determine the finger’s location. Capacitive touchscreens are smooth to operate and require only a light touch. They also allow the use of more than one finger, making “pinch and zoom” movements possible.
Most research now is going into improving capacitive devices and integrating the conducting layers into the screen to make thinner displays, says Jeff Han, a pioneer of multi-touch systems. His company, Perceptive Pixel, developed giant touchscreens used by some news organisations for election coverage and was sold to Microsoft in 2012. Mr Han says users should expect to see more ways to use fingers and gestures to operate touchscreens, along with additional haptic effects.
More capacitive screens will become pressure-sensitive. Apple's latest iPhone 6s responds to finger pressure with a process the company calls 3D Touch. The phone has another sensor below the screen which can detect a minute deformation in the glass when a finger is pushed against it. This allows additional actions by the user, such as pressing to preview a message or e-mail before opening it. Apple has also added haptic effects with something it calls a "taptic engine", in effect a refined tiny vibrator which provides subtle taps in response to certain finger movements.
To boost the responsiveness of touchscreens, alternatives to indium tin oxide are starting to be used. Although the material is transparent it is only moderately conductive, which can restrict just how responsive a screen is to touch. Metals, particularly gold and silver, are much better conductors, but not being transparent, they can interfere with the displayed image unless deposited in minute quantities—which reduces conductivity. One way around that problem has been developed by Dimos Poulikakos and his colleagues at ETH Zurich, a Swiss technical university. This involves building gold and silver capacitive grids as “nanowalls”, just 80-500 nanometres (billionths of a metre) wide. As the walls are perpendicular to the screen and two to four times taller than their width, the grid is highly conductive but almost invisible.Printing walls
Dr Poulikakos’s nanowalls are made with a new form of 3D printing. The process begins with gold or silver nanoparticles suspended in a solvent. This “ink” is drawn out of a tiny glass capillary tube by an electric field to form a drop which remains hanging onto the tip of the tube. By carefully balancing the composition of the ink and the electric field, the researchers have been able to get an even smaller droplet to form at the base of the attached drop. It is these secondary droplets which are used to print the nano walls.
Using nanoparticles means the cost of printing grids with precious metals, such as gold or silver, is not a concern, says Dr Poulikakos. Indeed, he reckons the “nanodrip” process would be a lot cheaper than current methods used to produce capacitive grids for touchscreens as these rely on costly clean rooms and vapour-deposition equipment, similar to that used to make computer chips. Nanodrip is now being scaled up for commercial use by a spin-off company called Scrona.
Other conductive materials that might be used to build touchscreens include graphene, a lattice of carbon atoms which, being only one atom thick, is essentially transparent. Researchers at the University of Manchester in Britain, where graphene was discovered, reckon the material can be used to make touchscreens which are flexible enough to roll up like a newspaper. This is because, unlike indium tin oxide, graphene is not brittle.
It will also become possible to operate touchscreens without actually touching them. Samsung has already employed tiny infra-red sensors just above the screen on some of its phones to detect hand gestures. Google is developing a miniature radar chip that could be embedded behind the screen itself to do much the same thing. The chip is supposed to be sensitive enough to pick up complex gestures, such as twirling a finger in a clockwise circle to increase the volume on a virtual dial or anticlockwise to reduce it.
Such technology could work on touchscreens in cars, too, without distracting drivers. BMW has developed a touchscreen that uses a camera in the roof of the car to recognise hand gestures. If the phone rings, say, you can simply point towards the screen to take the call; if it's the office, swiping your hand to the side will reject it. Add in fast-improving speech-recognition systems, such as Apple's Siri and Microsoft's Cortana, and the amount of time people spend jabbing, gesticulating and talking to their devices will only rise.