Abstract: A self-sensing wafer holder in a robot blade is described which includes a holder body of generally elongated shape adapted for carrying a wafer on a top surface and at least three sensors positioned on the holder body sufficiently away from each other to form a plane that is covered by the wafer. The at least three sensors can be of the capacitive type, the optical type or the weight sensing type. The wafer holder is capable of determining whether a wafer is properly seated on top of the holder and automatically stopping the motion of the robot blade when a misplacement is detected by utilizing a sensing circuit including logic gates.