Disclosed is a system for using pressure differential between completion fluid in an oil well and produced fluids to power downhole devices, including instruments and actuators. The rotor blade’s upper and lower wings are radially deflected from the central zone outwards. Alternatively, the outer spacer is molded over the inner elastic core, the core being in a neutral, compressed, tensioned or bent orientation during over molding of the spacer. A protective film is formed on the insulating film and the conductive line. The symmetric design of the servo pattern allows both a left-to-right and a right-to-left servo write and read back, thereby enabling use of a single master template in magnetic disk manufacture. By reducing temperature variations, changes in image intensity that are attributable to temperature variations are reduced.