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In the past 20 years,microfluidic technique has undergone fast progress,and various manipulation techniques for microfluids have been developed,including hydrodynamic,electrokinetic,microvalve/pump,centrifugation,and electrowetting techniques.Despite the successful and broad applications of these techniques,flexible and versatile liquid handling techniques are still in urgent need.Recently,on the basis of the previous DropLab system [1],we developed a sequential operation droplet array(SODA)system for performing fully-automated picoliter to nanoliter-scale droplet manipulation,analysis and screening [2].The SODA system has a simple setup consisting of a tapered capillary-syringe pump module and a two-dimensional oil-covered droplet array fixed on an x-y-z translational stage [2].An automated liquid handling strategy was developed with the SODA system using the programmable combination of the capillary-based liquid aspirating-depositing and the moving of the oil-covered droplet array,so-called "aspirating-depositing-moving"(ADM)mode.Complex and flexible liquid handling manipulations can be achieved with picoliter-scale precision,including liquid droplet assembling,generation,indexing,transferring,splitting and fusion.We applied the SODA systems in enzyme inhibitor screening [2],cell-based drug screening [3],protein crystallization condition screening [4],single cell microRNA quantification [5],as well as coupled them with high resolution analysis systems including liquid chromatography,capillary electrophoresis [6] and ESI-MS [7] for analysis of small amount of samples in the nanoliter to picoliter range.The SODA systems have showed significant improvement in reducing sample/reagent consumption(2-5 orders of magnitude),and exhibited unique high controllability,flexibility and versatility in performing complex microfluid manipulation.Therefore,we believe the SODA strategy will provide a novel microfluid manipulation technique for microfluidic systems,besides the previously-reported techniques,and could find broad applications in high throughput screening,biochemical analysis,fundamental research in biology and medicine,and clinical diagnosis.