Droplet-Based Microfluidics: Formation, Detection and Analytical Characterization

Microfluidics has been a critical technology for over two decades to study and manipulate fluids in microstructures. It has the potential to provide smart microdevices, which can change how modern biology, chemical synthesis, and point-of-care diagnostics are performed [1]. Microfluidics offers many advantages, including minute quantities of samples and reagents, compact ability, low cost, rapid, high resolution and sensitive analyses. Continuous microfluidics typically involves single-phase flow in microchannels, although traditionally liquids with macromolecules, microparticles or cells are also categorized in continuous microfluidics. Due to the small Reynolds number (0.01-100), Re= ULρ/μ, the flow is laminar in microfluidic devices, where U, L, ρ and μ stand for the velocity of the flow, the diameter of the capillary, density and viscosity of fluid flow respectively [2]. Continuous microfluidics suffers from less efficient and slow mixing in microchannels, molecular contamination of loss on the surface of the channels and Taylor dispersion of molecules alongside the microchannels. The Taylor dispersion leads the parabolic velocity movement of liquid inside microchannels, which involves two velocity regimes, i.e. at the walls and in the middle of the microchannel [2,3].