  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.
