Microfluidics is multidisciplinary by nature having fundamental roots in physics, biochemistry and engineering. Microfluidic platforms have been widely applied for chemical, biological and biomedical assays benefiting from their small size which translates to reduced sample reagents, shortened analysis time and high throughput. Most microfluidic platforms are single phase based where either liquid or gas is the carrier fluid though liquid is used much more often. This type of platform suffers slow mixing due to laminar flow nature, low throughput, and contaminations between different liquid streams and between liquid and solid walls which cause low repeatability and reliability.
Droplet-based two-phase microfluidic platform is an excellent alternative which can address these disadvantages. In this type of platform, droplets are encapsulated by another different phase, therefore, contaminations between droplets and between droplets and channel walls are eliminated. In addition, droplets are rotating when transported through the channel network which provides three-dimensional mixing overcoming the slow mixing problem. Most importantly, the throughput of droplet-based microfluidic platforms is magnitude higher than single-phase microfluidic platforms because droplets can be generated at kHz with minimum (1-3 %) variance in their size or volume and each droplet can be treated as one individual reactor. Therefore potentially, droplet-based microfluidic platforms could have kHz throughput provided each droplet can be manipulated as desired.
Both gas-liquid and two immiscible liquids (water and oil) systems have been employed to make liquid droplets in microfluidic platforms. In this talk, only the system employing two immiscible liquids to generate droplets is discussed. To successfully design and control droplet-based microfluidic platforms, several functions including droplet generation, droplet trafficking and droplet sorting must be understood, which will be the main focus of this talk.