an apparatus for holding and orienting a wafer includes a movable robot arm , and an end effector attached to an end of the robot arm , the end effector including a gripping mechanism which during operation holds and rotates the wafer about an axis that is perpendicular to the plane of the wafer , wherein the gripping mechanism comprises a first contacting member , and a second contacting member , and a drive member arranged to grip opposing edges of the wafer , and wherein the drive member comprises a first pair of rollers .