Printed Capacitive Multi-Touch Sensor Customizable With Scissors

Researchers from Germany's Max Planck Institute for Informatics and the MIT Media Lab introduced a printed capacitive multi-touch sensor at the 2013 ACM Symposium on User Interface Software and Technology (UIST) in St. Andrews, UK. The sensor can be cut to modify its size and shape and remain working. The researchers say that this direct manipulation allows an end-user to easily make real-world objects and surfaces touch-interactive, and to augment physical prototypes. The design of the printable circuitry makes the sensor robust against cuts, damages, and removed areas.

Transcript

00:00:04 in this work will present the first capacitive multi-touch sensor which remains working after being cut this enables users to easily tailor at the sensor to their specific needs people have always cut traditional materials for customizing them on the fly for its since paper cardboard or cloth advances in printed electronics now make it possible to add electronic circuitry to

00:00:29 these materials however if cut in almost all cases the electronic functionality breaks we propose another product for printed electronics make it robust to cutting this allows people to modify the shape of up here it's also when electronics are embedded for instance we envision an adhesive sense of oil end-users can cut this wall to virtually any shape and size to fit onto the

00:00:54 object this enables multi-touch input on real-world objects and surfaces for instance users can make their personal items or the furniture interactive we also envision that the sensors embedded in raw materials such as paper cardboard or plywood this enables people to create interactive models prototypes and paper craft which support multi-touch input in a conventional touch sensor a set of

00:01:21 electrodes is arranged in a regular 2-dimensional grid each electrode senses one touch point the electrodes are connected to a connector with a set of horizontal and vertical wires the grid does not robust to cuts and removed parts considered two wires got damaged since each wire addresses many electrodes damage of a wire results in large areas that are not sensitive

00:01:41 anymore we introduce novel physical wiring topologies for overcoming this problem the first layout for the stochiometry of a star on the connector which is used to tether the sensor sheet with the controller's place in the center Y is extends readily to the electrodes the sensor is printed on flexible substrate using conductive ink to guide the user at the front side

00:02:04 features lines that act as abstract representation of the underlying topology this topology supports a large variety of shapes including triangles rectangles and ellipses we propose a simple calibration step to normalize sensor readings from partially cut electrodes due to its star topology the sensor remains functional and supports

00:02:30 multi-touch input in the tree topology all electrodes are thorgan le connected to one stream of wires which is then connected to the controller 32 apologies support shapes that are not supported by the star and vice versa the multi touch sensor remains functional the shape can be further refined

00:03:03 and still supports multi-touch input since different typologies each have their own unique strengths and drawbacks combining them as well you will redundancy in dramatic robustness in this example we combine a star topology with a tree topology allows for more complex shapes again multi-touch input is supported the robustness of the sensor can be

00:03:35 further increased by connecting each electrode with two redundant wires while this requires the double amount of wires we contribute a novel coding scheme that requires a smaller number of redundant wires it is inspired from forward error correction which is used for a robust transmission of data and computer networks let's have a look at two electrodes each electrode has its own

00:03:55 wire in addition one shared redundant wire is added to both electrodes if the user touches an electrode if capacitance value can be read both at the Darragh wire and at the shared redundant wire if both electrodes are touched the value adds up this is because both electrodes act as parallel capacitors to avoid that the shared wire creates a short circuit between both electrodes we use an

00:04:19 interdigitated design for the electrodes results from an evaluation show that many convex cutouts such as rectangles triangles and ellipses are well supported both by the star and the tree topology the star topology performs slightly better than the tree and results in coverage trades of more than 95% no matter where they cut out us exactly placed on the sensor or hard

00:04:43 scale and rotated more complex shapes such as carve outs and connectors are less well supported by these basic topologies the coverage can be increased by combining several topologies if the shape is placed on the sensor sheet at a fixed location and orientation even complex shapes are supported with an average of more than 90 percent