A microfluidic platform for parallel synchronization of multiple droplets by ladder-like fluidic network

We propose a microfluidic platform where a dilution module to generate concentration gradient and a ladder-like fluidic network for a parallel synchronization of a droplet were integrated. The device consists of two layers: upper layer is for oil phase and lower layer for water phase. The desired concentration at the lower layer was achieved by means of controlled volumetric mixing ratios of two merging solution in a T-junction. By controlling channel length, fluidic resistances were adjusted. The water-in-oil droplets generated at lower layer were injected to the synchronization region where a top, middle, and bottom channel were interconnected among the three main channels. By a pressure difference caused from the droplets among main channels, the oil, carrier fluid, flows through the interconnection channels until the pressure in each channel was balanced automatically. The proposed device showed the feasibility of the synchronization of three droplets with 92% efficiency at the optimized flow rate condition. As the device enables passive synchronization of droplets with different concentrations, it has a potential to be integrated with a conventional droplet-based microfluidic platform for a reliability of mixing.