Competition between Local Collisions and Collective Hydrodynamic Feedback Controls Traffic Flows in Microfluidic Networks

Abstract

By studying the repartition of monodisperse droplets at a simple T junction, we show that the traffic of discrete fluid systems in microfluidic networks results from two competing mechanisms, whose significance is driven by confinement. Traffic is dominated by collisions occurring at the junction for small droplets and by collective hydrodynamic feedback for large ones. For each mechanism, we present simple models in terms of the pertinent dimensionless parameters of the problem.

Microfluidic breakups of confined droplets against a linear obstacle: The importance of the viscosity contrast

“…To study the physics of obstacle-mediated breakup, we work with planar microfluidic devices which consist of a drop generator based on a flow-focusing method [14], a dilution module [15] that enables control of the velocity of the drops without changing their size by infusing additional continuous phase, and a linear obstacle, placed in a rectangular microchannel of width w = 130 μm and height h = 45 μm [see Fig. 1(a)].…”

Encoding and controlling of two droplet trains in a microfluidic network with the loop-like structure

“…Fuerstman et al (2007) realized the operations of encrypting and decrypting signals within a microfluidic encoding/decoding loop device, by treating the droplet intervals as the coded signals. In those microchannel networks, the presence of junctions, bypasses and loops notably increase the complexity of the fluid dynamics of droplets, sometimes resulting in multiperiodicity and multistability (Jousse et al 2006;Belloul et al 2009;Jeanneret et al 2012;Wu et al 2012;Gleichmann et al 2014).…”

“…Schindler and Ajdari (2008) proposed a simplified model to find robust dynamical behavior of droplets and quantify its response to the changes in flow conditions and geometrical parameters of the microchannels. Belloul et al (2009) studied the competition mechanism between local collision for small droplets and collective hydrodynamic feedback for large ones. Wu et al (2014) studied bubble coalescence at the T-junction.…”

Traffic of pairs of drops in microfluidic ladder networks with fore-aft structural asymmetry

“…Such symmetric ladders are limited in functionality because the distance between pairs of drops have been shown to decrease at the exit only for constant inlet flow [11][12][13] . Since flexible manipulation of drop spacing in networks is crucial for passively regulating a variety of tasks including drop coalescence 14 , detection and storage, there is a need to design microfluidic ladders with multiple functionalities.From a fundamental perspective, the dynamics of drops in MLNs is distinct compared to the widely-studied microfluidic loops 5,7,13,15 . In loops, drops at junctions choose a given branch.…”

“…From a fundamental perspective, the dynamics of drops in MLNs is distinct compared to the widely-studied microfluidic loops 5,7,13,15 . In loops, drops at junctions choose a given branch.…”