Analysis of mixing in a helical microchannel

Examining fluid flow inside a monolithic, three-dimensionally oriented, microfluidic channel is experimentally challenging because it does not permit a laser sheet to be effectively applied; tracking microscopic tracer particles is difficult; and monolithic construction prevents access to any material inside. We overcome these problems with an approach which captures the flow both along the channel axis and in a plane perpendicular to it, yet lets us capture the flow pattern over a wide Reynolds number range. Our observations corroborate results from flow simulations.