University of Saarbrücken

Turning the Body into a Multi-Touch Surface

7. Mai 2018, 10:44 Uhr | Nicole Wörner
Da der Sensor in seiner Form einer Ohrmuschel ähnelt, klebt er bei der Versuchsperson direkt hinter dem rechten Ohr. Die Versuchsperson kann auf ihm nach oben oder nach unten streichen, um die Lautstärke zu regulieren. Das Streichen nach rechts und l
The sensor sticker can be placed behind the ear, for example.
© Universität des Saarlandes

Saarbrücken computer scientists have developed innovative skin sensors that can be used to control mobile devices from any part of the body. This turns the human body surface into a multi-touch surface.

Computer scientists at Saarland University have developed sensors that, for the first time, make it possible to detect touches on the body very precisely and from several fingers at once. The sensor, called "Multi-Touch Skin", is similar in construction to a touch display as it is known from smartphones. Two electrode layers, each arranged in columns and rows, form a kind of coordinate system when positioned  on top of each other, at whose intersection points the electrical capacitance is constantly measured. This decreases at the point where the fingers touch the sensor, as the fingers conduct electricity and drain charge. These changes are recorded at all points and thus also the touches of several fingers are detected.

To find the optimum balance between conductivity, mechanical robustness and flexibility, the researchers have investigated various materials. For example, if the following components are selected: silver as conductor, PVC plastic as insulating material between the electrodes, and PET plastic as substrate, the sensor can be printed in less than one minute using a standard household inkjet printer.

In order to be able to design the shape of the sensor as desired, the scientists developed special software for designers. In the computer program, the designer first draws the outer shape of the sensor, then he encloses the area inside the outer shape that is intended to be touch-sensitive. A special algorithm then calculates the best possible allocation of touch-sensitive electrodes,  covering as much area as possible within the specified region. The sensor is then printed.

How helpful this newly gained freedom of form is becomes particularly clear with a test prototype. Since the shape of the sensor resembles an auricle, it sticks directly behind the right ear of the test person. The tester can brush up or down on it to adjust the volume. Brushing to the right and left changes the song, while touching with the flat finger stops the song.

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