Researchers at Saarland University have developed a prototype sensor, called Multi-Touch Skin, which turns the user’s body into a touch screen.
The device (see Figure 1) looks similar to smartphone touch displays, consisting of two stacked electrode layers arrayed in rows and columns. The configuration creates a coordinate system that measures electrical capacitance at the areas of intersection.
When someone touches the sensor, capacitance is reduced. This occurs since fingers conduct electricity, and enable the charge to drain upon contact. The device registers these changes, and therefore has multi-touch capabilities.
The Saarland University researchers had to find the right material to facilitate ideal conditions for conductivity, flexibility, and mechanical robustness. After testing, silver was the chosen conductor, PET plastic was used for the substrate, and PVC plastic won the spot as the insulating material between electrodes.
According to the team, the sensor can be created within minutes using a household inkjet printer.
“So that we could really use the sensors on all parts of the body, we had to free them from their rectangular shape. That was an important aspect,” says Aditya Shekhar Nittala, doctoral researcher on the Saarland University team.
To achieve this, specialized software allows designers to mold their own sensor shapes. Users define the sensor’s outline, and denote which areas are to be touch sensitive within the program. After an algorithm creates an optimal layout, the sensor is printed.
Scientists created four Multi-Touch Skin prototypes. One design was placed on a participant’s right ear, which enabled music volume control with upward and downward swiping. Right and left finger movements changed the song selection and a single touch paused the track.
Next, the team hopes to further develop on-skin interfaces by creating more advanced sensor design programs that can capture multipole sensory modalities.