Broken Symmetries in Microfluidic Pillar Arrays are Reflected in a Flowing DNA Solution across Multiple Length Scales

TL;DR

This study investigates how the symmetry of microfluidic pillar arrays influences the formation of large-scale flow waves in viscoelastic DNA solutions, revealing control mechanisms relevant for microfluidic applications.

Contribution

It demonstrates the impact of pillar symmetry on wave formation and flow behavior in viscoelastic fluids within microfluidic arrays, advancing understanding of flow symmetry effects.

Findings

Flow waves depend on pillar symmetry

Wave onset varies with Deborah number and flow direction

Flow rate increases during wave formation

Abstract

Unlike Newtonian fluids, viscoelastic fluids may break time-reversal symmetry at low Reynolds numbers resulting in elastic turbulence. Furthermore, under some conditions, instead of the chaotic turbulence, large-scale regular waves form, as has been shown for DNA flowing in microfluidic pillar arrays. We here demonstrate how the symmetry of the individual pillars influences the symmetry of these waves, thereby contributing to the understanding of the origin of the waves and opening up for better control of the waves with relevance to applications such as microfluidic sorting and mixing. The onset of waves occurs at different Deborah numbers for flow in different directions through the same array. Because the onset of waves leads to an increase in flow rate for a given driving pressure, we observe an increase in diodicity within this range.