Computer aided design optimisation of microfluidic flow distributors

This study reports on a quantitative study of the influence of the most important geometrical design parameters for micro-machined flow distributors with uniform cross-section and filled with diamond-shaped pillars having their longest dimension oriented perpendicular to the axial flow direction. It was found that the shape of the bands eluting from the distributor improves with increasing aspect ratio (AR) of the pillars, both in terms of global warp and local axial dispersion. Increasing the AR from 5 to 25 reduces the distributor length needed to bring the maximal transversal velocity difference below 5% from 170 μm to 15 μm when using pillars with axial width of 5 μm. To solve the problem that high AR pillar distributors only have a limited number of exit points, and therefore produce bands with a strong local warp, one can conceive mixed size distributors, wherein a zone filled with several rows of very high AR pillars is followed by one or more zones consisting of pillars with a smaller AR. With such a design, the variance of the eluting bands can be reduced to only 30% of the variance of a single size distributor.