Introducing purely hydrodynamic networking functionalities into microfluidic systems

Microfluidics is a multidisciplinary field with practical applications to the design of systems, called lab-on-chip (LoC), where tiny volumes of fluids are circulated through channels with millimeter size and driven into structures where precise chemical/physical processes take place. One subcategory of microfluidics is droplet-based microfluidics, in which discrete volumes of fluids disperse into a continuous stream of another immiscible fluid, which acts as the droplet carrier. Droplets can then be moved, merged, split, or processed in many other ways by suitably managing the hydrodynamic parameters of the LoC. A very interesting research challenge consists in developing basic microfluidic structures that are able to interconnect specialized LoCs or, more generally, microfluidic machines (MMs), by means of a flexible and modular microfluidic network. The aim of this paper is to exploit the properties of droplet-based microfluidics to realize purely hydrodynamic microfluidic elements that provide basic networking functionalities, such as addressing and switching. We define some simple mathematical models that capture the macroscopic behavior of droplets in microfluidic networks, and use such models to design and analyze a simple microfluidic network system with bus topology. The study points out some tradeoffs that need to be accounted for when designing a microfluidic network, and proposes a first approach to the performance analysis of this kind of network, while listing a number of open research challenges that call for further study.