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Mobile Device Screens That Tap Back

Touchscreen system

Research engineers Sophie Nalbach, left, and Steffen Hau from Stefan Seelecke’s lab test the prototype system exhibited at Hannover Messe. (Oliver Dietze, Saarland University)

15 Mar. 2019. Engineers in Germany designed screens for mobile phones and tablets that not only feel touch pressure, but can also return pulses or vibrations to users’ fingers. A team from Saarland University’s Center for Mechatronics and Automation Technology, or Zema, in Saarbrücken plans to demonstrate the technology on 1 to 5 April at the Hannover Messe, an annual technology trade show in Germany.

Researchers from the Intelligent Material Systems Lab in Zema, led by engineering professor Stefan Seelecke, is seeking to provide more sensory mechanisms to mobile devices that increase their ability to interact with users. Seelecke’s lab studies electroactive polymers, thin sheets of plastic like common household plastic wraps, with electronic properties that both sense and respond to touch with tactile actions and motions that can be felt by the users.

Seelecke and colleagues add this electronic capability to plastic films by printing a thin conductive layer on the polymers. This conductive property enables the film to expand or contract in response to changes in the current. These changes in current can then be programmed to enable plastic films to emit complex or precise tactile signals, such as emulating a heart beat or vibrating in high-frequency oscillations. The lab also writes algorithms to provide more precise and complex control over the tactile signals given through the plastic film.

“We use the film itself as a position sensor and this imparts sensory properties to the display,” says engineering researcher Steffen Hau in a university statement. “There’s no need for any other sensors.” Hau adds, “This means that we always know exactly how the film is deforming at any specific moment.”

The ability to not only sense the position of fingers on the screen, but also respond with tactile signals makes it possible for users to interact with a mobile device strictly through the screen. For example, virtual buttons can be added to the screen, with tactile signals directing users’ fingers to different positions on the surface.

Seelecke notes the electroactive polymers use inexpensive, everyday materials. “As this technology does not rely on rare earths or copper,” says Seelecke, “it can be manufactured cheaply, it consumes very little energy, and the polymer films are astonishingly light.”

The Intelligent Material Systems Lab built smartphone and tablet prototypes with electroactive polymer screens that it plans to demonstrate in Hannover. At the trade show, the researchers hope to attract commercial and industrial partners to help take the technology to market.

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