In accordance with one aspect of the exemplary embodiments, a substrate transport apparatus is provided comprising a drive mechanism, a movable arm assembly connected to the drive mechanism, an end effector connected to the arm assembly. A chuck for holding a substrate is mounted on the end effector and having a movable edge gripper with a contact surface and an edge of the substrate may be gripped by actuating the movable edge gripper to engage the substrate with the contact surface. The apparatus further comprising a motion sensor for providing a signal to actuate the movable edge gripper to close and open the moveable edge gripper for capturing and releasing the substrate.