A system is described for automatic retrieval of microplates from a carousel. The system includes an effector arm that retrieves a selected microplate from the carousel, a microplate retainer that receives the selected microplate from the effector arm, and a controller that directs the effector arm to the carousel for retrieval of the selected microplate and directs the effector arm to the microplate retainer so that it may receive the selected microplate. The carousel may revolve around a vertical axis. A system also is described for washing depositing elements used to spot biological materials on a substrate. Graphical user interfaces also are described for enabling a user to determine which microplates will be used to provide biological probe materials, and in what patterns those probe materials should be deposited on the substrate. The interfaces enable the user to place multiple fractions of biological materials on a same location on a substrate. Also described are graphical user interfaces that present a user with the options to select a first microplate having a plurality of wells, associate at least one probe material with one or more of the wells, and associate one or more locations on one or more substrates with the one or more wells.