What is the minimal capacitor (capitor type/size/capacity) needed to fool a capacitive touch screen?
Capacitive touch screens are factory tested with a metal rod of a specific diameter (6mm, in my experience). I do not know what the minimum length of the rod can be, but it does not need to be as long as a finger. The rod does not need to be attached to any other circuitry or grounded. The capcitive touch mechanism works by responding to changes in the electrical properties of space in the area very close to the screen. If the diameter of the rod is too small, it will not be detected. For example, a nail or typical electric wire is too narrow for detection.