Based on what I have gathered so far, I don't see why a micro-scale generator wouldn't work, but then again I am a geographer with modest calculus skills. My biggest problem is not knowing how much I don't know, and I am hoping some kind and wise soul on PF can cure my ignorance. Let's say I need to generate 3.5 volts/0.5 amps to light up an LED bright enough to be visible outside in daylight, but the micro-generator must fit in a cylinder ~ 2.5mm diameter and ~4.0mm to 4.5mm in length. I was thinking of a design that would exploit "printed" circuitry and "print" a serpentine "coil" consisting of say 20 windings each 4.0mm long (roll the printed circuit into a tube that's 2.5mm in dia.). If I took a diametric rod magnet that was 2.4mm in diameter and 4.0mm long and placed it concentrically inside the cylindrical coil, the distance between the magnet and the windings would be 0.5mm. Unless I've missed something, the remaining parameters needed to calculate output would be the Gaussian strength of the magnet and the number of times the magnetic field cycles through the coil in a second (to determine voltage), and the cross section area of a winding (to determine amperage). Is there a mathematical relationship between the magnet's Gauss rating and the rate of flux change that would satisy the volage requirement? If so, I would need help deriving a function to express that relationship. How do I determine the minimum area of a winding's cross section needed for 0.5 amps (I don't know how "thick" I can print)? Thanks in advance!