Printable, multi-touch sensors consumers can cut with scissors

http://embodied.mpi-inf.mpg.de/files/2012/11/ACuttableMultiTouchSensor.pdf

Max Planck Institute researchers and the MIT Media Lab have developed printable, multi-touch sensors that are printed with e-ink and can be cut with scissors.  A new circuit layout makes it robust against cuts, damage, and removed areas.  By customizing and pasting such a sensor, one can make every surface interactive, including the wristband of a watch, a fabric or an object.  This implies many digital health and fitness applications.

The scientists use “printed electronics” – electrical components and devices which are printed. The approach is similar to that of inkjet printers. Instead of printing with normal ink, electrically-functional electronic ink is printed on flexible, thin films called substrates.

In the circuit layout, the wires run horizontally, vertically, and parallel to each other. At the intersection of one parallel and one horizontal layer are the touch-sensitive electrodes. Via the wires they are connected to a controller. This type of layout requires only a minimal number of wires, but is not robust. Since each wire addresses several electrodes, a small cut has a huge effect: many electrodes become unusable and possibly large sensor areas do not work anymore. “It was not easy to find an alternative layout, robust enough for our approach” said lead developer Simon Olberding. They took their inspiration from nature, looking at the human nerve system and fungal root networks, and thus came up with two basic layouts. The “star topology” has the controller in the center. It is connected to every electrode separately. The “tree topology” also has the controller in its center connected to each electrode separately. But the wires are bundled similarly to a tree structure. They all run through a vertical line in the middle and then branch off to reach their electrodes.