Modeling particle flow and blockages in microfluidic channels supported by periodic posts

One potential problem with microfluidic systems is the accumulation of particles and fluid bubbles inside chambers and other structures, which causes distortion in fluid flow potentially leading to device or system failure. Microfluidic channels and chambers that utilize a “cathedral-ceiling” arrangement, whereby periodic posts support the tops of the channels, have been suggested to improve defect tolerance over arrays of parallel channels through the provision of multiple paths during localized blockage formation. This paper builds on our prior investigations through development of a combined rule-based defect placement system and Monte Carlo method for modeling the fluid dynamics and blockage formation based on the likelihood of blockages forming in areas of high particle traffic and low flow. Our COMSOL model generates 150 randomly (normal) distributed particle streamlines. Coordinates along these streamlines are crossexamined to find the lowest flow areas, which are deemed likely points for blockage formation. MATLAB filtering then determines which microfluidic channel areas are most likely to obstruct based on particle population density. This process is iterated as blockages form, creating new streamline patterns, which in turn indicate placements for new blockages, and modified geometry for successive modelling iterations. This semi-automated method has enabled us to predict where the particles may accumulate and how this progressive block formation may change system pressure and flow. Results obtained support the findings of significantly increased lifetime expectancy of microfluidic chambers with periodic posts compared to arrays of parallel channels, while also providing greater insight into where blockages may form in the cathedral-ceiling type geometry.