Engineers Give Touch Screens a Third Dimension: Buttons Knock and Vibrate at the Fingertips

third dimension
The first touchscreen that taps back: Engineers Sophie Nalbach and Steffen Hau from Stefan Seelecke's team test the prototype system that will be exhibited at Hannover Messe. Credit: Oliver Dietze

By tapping or vibrating, the display can guide the finger of the smartphone user through the menu. Or to buttons and buttons that arise at any point and disappear again. Professor Stefan Seelecke and his team from the University of the Saarland have developed a film that gives touchscreens a third dimension. The lightweight, thin silicone film holds steplessly different positions and heights; she can knock, push, push and vibrate. It also has sensor properties and thus becomes the sense organ of the respective device.

At the Hanover Fair, the engineers are looking for partners to further develop the technology for the practice: from 1 to 5 April at the Saarland research stand (Hall 2, Stand B 46).

If the smartphone user moves his fingertip over the display, there is suddenly a knock at one point. Underneath, a button is created as if by magic. Or the user follows the signal that guides his finger, and he finds the button this way. With the new technology developed by the engineering team of Professor Stefan Seelecke at the Department of Intelligent Material Systems of the University of Saarland and the Center for Mechatronics and Automation Technology, buttons can emerge and disappear anywhere on the screen as needed. By vibration, knocking or bumping the finger tip, the display can guide its user to them. This opens up new possibilities for computer games, internet searching and also for navigation devices.

An unspectacular silicone film at first glance – not unlike the commercial cling film – lays the foundation for a new generation of displays. “The film is a so-called dielectric elastomer,” explains Professor Stefan Seelecke, whose working group has received several awards at international conferences.

The engineers print an electrically conductive layer on a wafer-thin plastic membrane. This allows them to apply an electrical voltage: the “electroactivity” of the film means that they can contract in one direction and stretch in the other direction. “Due to the electrostatic forces of attraction, the polymer compresses, for example, and expands outward,” explains Steffen Hau, a graduate engineer from Seelecke’s team. If the researcher modifies the electric field, the film performs a wide variety of choreographies and gives any signals: from high-frequency vibration to specific impulses such as a heartbeat to stepless lifting movements. In her prototype, which the scientists show at the Hannover Messe, They combined the slides with a smartphone display. Not only do they create virtual buttons, they also open up additional functions for the display.

With a rule on algorithms, the piece of plastic becomes a technical component that engineers can use to control. “We use the film itself as a position sensor. The display also has sensory properties. We do not need further sensors, “says Steffen Hau. The researchers can assign each individual position of the foil exactly to the corresponding measured values ​​of the electrical capacitance. “As a result, we always know how the polymer is deforming. With the measured values ​​of the electrical capacitance we can infer the respective mechanical deflection of the foil. By changing the electrical voltage, we can control the foil precisely, “explains Hau. In a control unit, the motion sequences can be calculated and programmed exactly.

“Because the technology works without rare earth or copper, it is cheap to produce, uses very little energy and is very light,” added Professor Seelecke. The elastically deformable plastic films are still the result of application-oriented research. The engineers are now looking for partners from industry and companies at Hannover Messe to bring their process into production.