These are built by sandwiching a piece of porous, spacing fabric (e.g. tulle) between two sheets of piezoresistive fabrics (from Eeonyx). For the square pad depicted below rectangular sheets are placed at right angles and wrap around the frame. On the inside they are stapled to a conductive strip on each edge. The four edges are wired to the analog inputs of a suitable microcontroller, e.g. uOSC, Teensy or Arduino.
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