Braess's paradox and programmable behaviour in microfluidic networks

TL;DR

This paper demonstrates that microfluidic networks can be designed to exhibit nonlinear behavior, enabling flow control and routing through pressure manipulation, including a fluid analog of Braess's paradox, which could lead to integrated control mechanisms.

Contribution

The authors introduce microfluidic networks with nonlinear pressure-flow relations that enable flow switching and routing, including a fluid Braess's paradox, advancing integrated control in microfluidics.

Findings

Microfluidic networks can exhibit nonlinear pressure-flow behavior.

Closing a channel can increase total flow rate (Braess's paradox).

Scalable flow routing with multiple switches is possible.

Abstract

Microfluidic systems are now being designed with precision to execute increasingly complex tasks. However, their operation often requires numerous external control devices due to the typically linear nature of microscale flows, which has hampered the development of integrated control mechanisms. We address this difficulty by designing microfluidic networks that exhibit a nonlinear relation between applied pressure and flow rate, which can be harnessed to switch the direction of internal flows solely by manipulating input and/or output pressures. We show that these networks exhibit an experimentally-supported fluid analog of Braess's paradox, in which closing an intermediate channel results in a higher, rather than lower, total flow rate. The harnessed behavior is scalable and can be used to implement flow routing with multiple switches. These findings have the potential to advance development of built-in control mechanisms in microfluidic networks, thereby facilitating the creation of portable systems that may one day be as controllable as microelectronic circuits.