A robotic or mechanical hand includes a number of infrared distance sensors, an alarm unit, a driving unit, and a processing unit. Preferred magnetorheological fluids of the present invention comprises polarizable iron particles, a carrier fluid, and optionally an additive. A recording-medium starting section activates the recording medium detected by the detector to be in an accessible state. A first outlet opening is formed in the enclosed containment body. Silicon substitutional impurities are appropriate for accomplishing such a segregation. By swinging out of the movable arm against the carrier, the carrier is turned out and the given tray is separated from the others and it can thus be served by the manipulator.