Automated Microfluidic Screening Assay Platform Based on Drop Lab

This paper describes Drop Lab, an automated microfluidic platform for programming droplet-based reactions and screening in the nanoliter range Drop Lab can meter liquids with picoliter-scale precision, mix multiple components sequentially to assemble composite droplets, and perform screening reactions and assays in hnear or two dimensional droplet array with extremely low sample and reagent consumptions A novel droplet generation approach based on the droplet assembling strategy was developed to produce multicomponent droplets m the nanoliter to picoliter range with high controllability on the size and composition of each droplet. The DropLab system was built using a short capillary with a tapered tip, a syringe pump with picoliter precision, and an automated liquid presenting system The tapered capillary was used for precise liquid metering and mixing, droplet assembling, and droplet array storage Two different liquid presenting systems were developed based on the slottedvial array design and multivell plate design to automatically present various samples, reagents, and oil to the capillary Using the tapered tip capillary and the picoliter-scale precision syringe pump, the minimum unit of the droplet volume in the present system reached similar to 20 pL Without the need of complex microchannel networks, various droplets with different size (20 pL-25 nL), composition, and sequence were automatically assembled, aiming to multiple screening targets by simply adjusting the types, volumes, and mixing ratios of aspirated liquids on demand The utility of DropLab was demonstrated in enzyme inhibition assays, protein crystallization screening, and identification of trace reducible carbohydrates