How cool is this? An Afrotech forumer made a functional computer touchpad out of paper and a little graphite drawn on with the tip of a pencil. The key: Graphite actually functions as a decent electrical conductor.
There isn’t much to explain here. It just uses pencil graphite on paper as a kind of two dimensional potentiometer. Four voltage dividers between 5v, 2M ohm resistors, the paper, and my grounded finger feeds signals from each corner into an Arduino. The Arduino does some insufficient math and spits out mouse coordinates that are not linear.
Shakycammed but still cool demo video below: