A wafer handling system comprising: a robot arm including: a base; a first movable link, a first end of the first movable link rotatably connected to the base via a first rotational joint; a second movable link, a first end of the second movable link rotatably connected to a second end of the first movable link via a second rotational joint; a first rotational drive transfer mechanism including a first pulley, a second pulley, and one or more first belts spanning between the first pulley and the second pulley, wherein: the second pulley is fixedly connected with the second movable link, and the first rotational drive transfer mechanism is configured such that rotation of the first pulley relative to the first movable link causes the second pulley and the second movable link to rotate relative to the first movable link about a center axis of the second rotational joint; a first motor, the first motor located in the base and having a rotational output connected to the first movable link and configured to drive the first movable link; a second motor, the second motor located in the base and having a rotational output connected to the first pulley and configured to drive the first pulley; a first rotational encoder with a first portion fixedly connected with the base and a second portion fixedly connected with the first movable link; and a second rotational encoder with a first portion fixedly connected with the first movable link and a second portion fixedly connected with the second movable link, wherein: interior spaces of the base, the first movable link, and the second movable link are in fluidic communication with one another within the robot arm, the first rotational joint and the second rotational joint are both equipped with vacuum-tight seals, the first rotational joint is hollow along its centerline and a portion of a wiring connected to the second encoder is disposed in the hollow of the first rotational joint, each of the one or more first belts is a v-belt, a flat belt, a toothed belt, or a round belt, and each of the one or more first belts is made from a material that includes a polymeric material or a polymeric material in combination with a textile. a base; a first movable link, a first end of the first movable link rotatably connected to the base via a first rotational joint; a second movable link, a first end of the second movable link rotatably connected to a second end of the first movable link via a second rotational joint; a first rotational drive transfer mechanism including a first pulley, a second pulley, and one or more first belts spanning between the first pulley and the second pulley, wherein: the second pulley is fixedly connected with the second movable link, and the first rotational drive transfer mechanism is configured such that rotation of the first pulley relative to the first movable link causes the second pulley and the second movable link to rotate relative to the first movable link about a center axis of the second rotational joint; the second pulley is fixedly connected with the second movable link, and the first rotational drive transfer mechanism is configured such that rotation of the first pulley relative to the first movable link causes the second pulley and the second movable link to rotate relative to the first movable link about a center axis of the second rotational joint; a first motor, the first motor located in the base and having a rotational output connected to the first movable link and configured to drive the first movable link; a second motor, the second motor located in the base and having a rotational output connected to the first pulley and configured to drive the first pulley; a first rotational encoder with a first portion fixedly connected with the base and a second portion fixedly connected with the first movable link; and a second rotational encoder with a first portion fixedly connected with the first movable link and a second portion fixedly connected with the second movable link, wherein: interior spaces of the base, the first movable link, and the second movable link are in fluidic communication with one another within the robot arm, the first rotational joint and the second rotational joint are both equipped with vacuum-tight seals, the first rotational joint is hollow along its centerline and a portion of a wiring connected to the second encoder is disposed in the hollow of the first rotational joint, each of the one or more first belts is a v-belt, a flat belt, a toothed belt, or a round belt, and each of the one or more first belts is made from a material that includes a polymeric material or a polymeric material in combination with a textile. interior spaces of the base, the first movable link, and the second movable link are in fluidic communication with one another within the robot arm, the first rotational joint and the second rotational joint are both equipped with vacuum-tight seals, the first rotational joint is hollow along its centerline and a portion of a wiring connected to the second encoder is disposed in the hollow of the first rotational joint, each of the one or more first belts is a v-belt, a flat belt, a toothed belt, or a round belt, and each of the one or more first belts is made from a material that includes a polymeric material or a polymeric material in combination with a textile.