Using symmetry to control viscoelastic waves in pillar arrays

Abstract

Leveraging symmetry of pillar arrays to control instabilities and mixing of high-concentration DNA solutions.

Geometry-Dependent Elastic Flow Dynamics in Micropillar Arrays

“…Here, a recent example of canopy waves resembles our waves, except they are observed as a movement of the pillars rather than fluctuations in concentration [49]. It would be highly interesting to explore these types of waves for different geometries, degrees of order, and symmetry, just like we demonstrate here and have demonstrated previously [11,23].…”

“…By altering the pore structure geometry, the flow dynamics changes, which could be exploited in important applications by e.g., enhancing or suppressing flow mixing in microfluidic devices with relevance for transport of complex fluids, sorting of biomedical samples and enhanced chemical reactions by controlled mixing of reagents. Specifically, for mixing applications, the waves have been shown to lead to mixing [23] consistent with what has been shown for elastic turbulence [5,54]. For sorting and unmixing applications, one approach is to suppress the waves by carefully leveraging the effects of symmetry as we reported recently [23], or by randomizing the array sufficiently to suppress the waves, but not excessively such that the sorting mechanism would be hindered.…”

“…In a recent publication [23], we show that the characteristics of the waves can be determined to a large part by the shape of the pillars. In the paper, we also showed that the waves can be suppressed by alternating the pillar geometry such that the necessary conditions for the waves cannot be reached.…”

“…This work and our previous work [11,22,23], all explore variations of the design that take place in the plane of the device, i.e., in a 2D context with weak confinement where the ratio of the pillar size and the device depth is O(1). With both inertial turbulence [41] and viscoelastic fluctuations [42][43][44][45] exhibiting flow patterns that depend on dimensionality, a natural next step would be to investigate the effect of vertical confinement.…”

“…We have recently reported the formation of regular macroscopic waves [11] in highconcentration DNA solutions flowing through quadratic arrays of cylindrical pillars in microfluidic channels and demonstrated that these waves interfere in the sorting of DNA in microfluidic devices based on deterministic lateral displacement (DLD) [22]. We also noticed that the formation of waves is highly sensitive to any disorder in the array as well as to the symmetry of the pillars [23]. We introduce arrays with hexagonal geometry here due to their relevance for pulsed-field separation of DNA [24,25].…”