Abstract: A robotic liquid handling system is developed for dispensing highly viscous reagent with nanoliter volumes in membrane protein crystallization. The system construction is introduced, and it mainly consists of motion control module, dispensing control module, droplet volume detection module. Highly viscous reagent can be dispensed in nanoliter through controlling the dispensing control module and the motion control module correctly, and the volume of micro-drop can be detected by means of robotic vision technique. The factors that influence the successful delivery of nanoliter volumes of highly viscous reagent are discussed through analysis of the dispensing process. And the two critical values that the dispense height should be kept are derived. Three kinds of reagent with different viscosity are used for dispensing experiments to verify the theoretical results. The accuracy of the system has been shown to be below 7%, and the coefficient of variance (CV) has been shown to be below 10%.

Key words: Drop volume detection, Liquid dispensing, Viscous reagent