Concentration on demand – A microfluidic system for precise adjustment of the content of single droplets

We present a novel microfluidic system that produces the required concentration of a reagent in a single droplet or that produces a sequence of droplets with a defined periodic distribution of concentrations. We use digital algorithms that, through a series of simple operations, such as merging and splitting droplets, ensure superior precision, repeatability and flexibility in concentration setting. Unlike Digital microfluidic (DMF) systems based on electrowetting on dielectric (EWOD) commonly used to implement digital algorithms in the droplet world, our approach is based on much more available channel-based microfluidics operated by programmable syringe pumps. Furthermore, the small footprint of our system makes it easy to integrate with other structures of microfluidic networks. Thus, this technique is a comprehensive component that can be built into the microfluidic networks executing laboratory analytical tasks in chemistry or biology to enrich their performance and offer new functionalities.