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Since electronic paper consists of cells, inside which is the 'ink' used to show images - it could be made touch sensitive by adding a grid of extremely thin wires to the back of it (one layer of horizontal wires, separated from a layer of vertical wires).
Each wire will cover the length, or width
of the paper, and will have areas where the wire protrudes through to the front surface. A wire which lies horizontally along it will have an upwards protrusion through every other space between cells, likewise, a wire which lies vertically will have a protrusion for every other space.
When something comes in contact with a horizontal and a vertical wire (a fingertip, or a conductive stylus) a small current will pass from the vertical wire - through the object touching it and into the horizontal wire, completing the circuit and allowing the area being touched to be specified.