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Tom Cadera has already witnessed many trends in machine operation. In his office he has assembled a small collection of human machine interfaces (HMI) dating from various decades. “Some companies still work with interfaces developed in the early 90s,” explains Cadera. Usability has meanwhile become a competitive factor for many machine manufacturers. Not all industrial users are happy with touch-only displays. “We humans want to interact physically with products, like to feel the controls and get clear haptic feedback. I think we literally want to ‘get to grips’ more. I think that interaction will become more three-dimensional in the long term,” maintains Cadera.

Professor Stefan Seelecke and his team from Saarland University would definitely concur with Cadera’s market assessment. They have developed a film that gives touchscreens a third dimension. The thin, featherweight silicone membrane maintains infinitely variable positions and heights; it can pulse and vibrate. It also has sensor properties and thus functions as the sensory organ of the respective device.

When the user moves his fingertip over the display, he feels a ‘pulse’ at a predefined point. As if by magic, a button appears on the display. Alternatively, the user is guided to the button by means of signals generated in the display surface. With the aid of this new technology – developed by the engineering team at the Intelligent Material Systems Lab at Saarland University and the Centre for Mechatronics and Automation Technology – buttons can appear and disappear anywhere on the display as required. The display directs the user by means of vibrations and pulses that can be detected by the fingertips.

A silicone film (unspectacular at first sight, more or less similar to commercial cling film) lays the foundation for a new generation of displays. “The film is a so-called dielectric elastomer,” explains Seelecke, whose application had already received several awards at international conferences before being presented at HANNOVER MESSE.

The engineers have succeeded in printing an electrically conductive layer onto an ultrathin plastic membrane. This enables them to apply an electrical voltage: The electrical activity of the film means that it can shrink in one direction and stretch in the other.

“Due to the electrostatic attraction forces, for example, the polymer contracts and expands,” explains Steffen Hau, engineer and a member of Seelecke’s team. In response to changes in the electric field the film performs a wide variety of ‘choreographies’ and emits various signals: for example, high-frequency vibrations, specific pulses such as a heartbeat, as well as stepless lifting movements. In their prototype (displayed at HANNOVER MESSE) the research team have combined the films with a smartphone display. This has paved the way to virtual push-buttons and an enhanced range of functions.

Technology does not depend on rare earths

An algorithm-based control system has transformed a piece of plastic into a sophisticated technical component. “We use the film as a position sensor. We don’t need any additional sensors,” explains Hau. The researchers can assign each individual position on the film to the acquired electrical capacitance data. “This means that we always know how the polymer is currently deforming. On the basis of the electrical capacitance we can deduce the respective mechanical deflection of the film. By changing the electrical voltage we can precisely control the film,” adds Hau. The motion sequences are precisely computed and programmed in a control unit.

The elastically deformable plastic films are the result of applications-oriented re-search. However, the research team is looking for industrial partners. The touchscreen has acquired a third dimension.

3D touch and haptic feedback will be a determining factor in future human-machine interfaces. But the push-button will probably be around in industry for a long time to come. Cadera’s HMI collection makes this impressively clear.