A gripper applied in a transport mechanism for transporting a wafer is provided. A convex portion of the dielectric layer covers at least one electrode. A portion of the electrode inserted into the space may be coated with a protective layer to prevent a chemical reaction of between the electrode and the sulfur. The second glass panel has a third surface facing the second surface and a fourth surface opposite the third surface. The client looks-up objects and makes NAS requests to the source file server using switch file handles. The apparatus includes a first voltage receiver disposed on a first side in reference to the print medium, a second voltage receiver disposed on a second side opposite the first side, a voltage supply unit adapted to apply the voltage selectively to the first voltage receiver and to the second voltage receiver, and a voltage adjustment unit adapted to compensate for variations of the voltage.