Droplet Microfluidic System with On-Demand Trapping and Releasing of Droplet for Drug Screening Applications

96-Well plate has been the traditional method used for screening drug compounds libraries for potential bioactivity. Although this method has been proven successful in testing dose response analysis, the microliter consumption of expensive reagents and hours of reaction and analysis time call for innovative methods for improvements. This work demonstrates a droplet microfluidic platform that has the potential to significantly reduce the reagent consumption and shorten the reaction and analysis time by utilizing nanoliter-sized droplets as a replacement of wells. This platform is evaluated by applying it to screen drug compounds that inhibit the tau-peptide aggregation, a phenomena related to Alzheimer's disease. In this platform, sample reagents are first dispersed into nanolitre-sized droplets by an immiscible carrier oil and then these droplets are trapped on-demand in the downstream of the microfluidic device. The relative decrease in fluorescence through drug inhibition is characterized using an inverted epifluorescence microscope. Finally, the trapped droplets are released on-demand after each test by manipulating the applied pressures to the channel network which allows continuous processing. The testing results agree well with that obtained from 96-well plates with much lower sample consumption (similar to 200 times lower than 96-well plate) and reduced reaction time due to increased surface volume ratio (2.5 min vs 2 h).