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Touchscreens go 3D with buttons that pulsate and vibrate under your fingertips

Professor Stefan Seelecke and his team at Saarland University have developed a film that gives touchscreens a third dimension.​

New technology developed at the Intelligent Material Systems Lab at Saarland University and at ZeMA (Center for Mechatronics and Automation Technology) in Saarbrucken enables buttons to appear and disappear at any point on the touchscreen of an IT device.

By generating vibrations, pulses or individual jolts that are felt by the user’s fingertip, the screen can guide the user’s finger to a virtual button at any required location on the display. This functionality opens up a whole range of options for computer games, internet searches and for satnav devices.

The material the film is made from is known as a dielectric elastomer.

The engineers in Seelecke’s team print an electrically conducting layer onto an extremely thin polymer membrane on to which they apply an electric voltage. Because the film is ‘electroactive’, it contracts in one direction and expands in the other when a voltage is applied to it.

"As a result of electrostatic attractive forces, the polymer film can, for example, be squeezed vertically, causing it to expand outwards," explained Steffen Hau, a PhD engineer working in Seelecke’s team.

If the researchers alter the electric field, the film responds by performing complex choreographies and produces tactile signals that range from high-frequency oscillations to pulsing motions like a heart beat or continuous variable flexing motions. Using intelligent algorithms, the team have been able to transform a piece of polymer into a technical component whose behaviour can be precisely controlled.

"We use the film itself as a position sensor and this imparts sensory properties to the display. There’s no need for any other sensors," said Steffen Hau.

"The research team can precisely assign any change in the position of the film to a change in the film’s capacitance, which means we always know exactly how the film is deforming at any specific moment. By measuring the capacitance of the dielectric elastomer, we can infer the exact amount of mechanical deformation in the film. By changing the applied voltage, we can precisely control the shape of the film," explains Dr. Hau.

Any required sequence of motion can be calculated and programmed in the control unit.

"As this technology does not rely on rare earths or copper, it can be manufactured cheaply, it consumes very little energy and the polymer films are astonishingly light," added Professor Seelecke.

Neil Tyler

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