Introducing purely hydrodynamic networking mechanisms in microfluidic systems

Abstract

Abstract-Microfluidic is a multidisciplinary field with practical applications to the design of systems, called Lab-on-aChip (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 microfluidic is droplet-based microfluidic, which disperse discrete volumes of fluids into a continuous stream of another immiscible fluid, which act as 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 able to interconnect specialized LoCs by means of a flexible and modular microfluidic network. The aim of this paper is to exploit the properties of dropletbased 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.

Simulating "Macroscopic" Behavior of Droplet-Based Microfluidic Systems

“…As a consequence, the resistance of the selected outlet will be increased to R 1 + ρ where ρ is as in (9). If the increased resistance is larger than the resistance R 2 of the other outgoing branch, a second droplet closely following the first one will switch into the secondary outlet.…”

“…Each droplet can indeed be represented as an additional resistor with resistance given by (9), connected in series to the resistor representing the channel that contains the droplet. A pictorial representation of the basic components of a microfluidic system and their electrical counterparts is shown in Fig.…”

“…For any further detail, please refer to [9], [10]. Note that, hereafter we assume microfluidic channels with equal rectangular section, having width w and height h, unless otherwise specified.…”

“…A first attempt along this direction was made in [9], [10], where the authors introduced some approximate equations to derive the hydraulic resistance of a channel as a function of its geometry and the characteristics of the fluids, and the resistance variation due to the presence of dispersed droplets in the channels. Based on those simple formulas, we here propose a simple mathematical model that captures the "macroscopic dynamic behavior" of a microfluidic network, i.e., the motion of the droplets in the circuit.…”

Transmitting information with microfluidic systems

“…In particular, we focus on the droplet generation mechanism since it is at the basis of our communication scheme. For further details concerning microfluidic issues, please refer to [8], [9].…”