Abstract: A rotor assembly includes a rotor plate to rotate around a first axis; a bucket rotatably attached to the rotor plate and to rotate around a second axis; and a stop plate to rotate around the first axis relative to the rotor plate between an open position and a closed position, when in the closed position, the stop plate is to engage the bucket to fix an angular position of the bucket relative to a plane of rotation of the rotor assembly.

Abstract: An apparatus includes a robotic system providing movement in three orthogonal directions to an arm operable to receive a pipette tip and to facilitate movement of fluid into and out of the pipette tip. In addition, the apparatus can include a tray for receiving pipette tips, receptacles for receiving tubes, an apparatus for forming an emulsion, a device for forming particles that include copies of the polynucleotide, a device for enriching the particles and an apparatus for loading such particles onto a sensor array. The apparatus can further include receptacles for holding containers of reagent solutions. Optionally, the robot can include a gripper arm in addition to the pipette receiving arm.