A microfluidic chip integrated with droplet generation, pairing, trapping, merging, mixing and releasing

Developing a microfluidic chip with multiple functions is highly demanded for practical applications, such as chemical analysis, diagnostics, particles synthesis and drug screening. This work demonstrates a microfluidic chip integrated with a series of functions including droplet generation, pairing, trapping, merging, mixing and releasing, and controlled entirely by liquid flow involving no electrodes, magnets or any other moving parts. This chip design is capable of trapping and merging droplets with different content on demand allowing the precise control of reaction time and eliminates the need for droplet synchronization of frequency, spacing or velocity. A compact model is developed to establish a set of design criterion. Experiments demonstrate that fast mixing in the merged droplets can be realized within several seconds benefiting from the flow fluctuation induced by droplets coming or leaving the trapping region. Additionally, it allows a concentration gradient of a reagent to be established. Finally, this design is applied to screen drug compounds that inhibit the tau-peptide aggregation, a phenomenon related to neurodegenerative disorders.