Mr. Mahyar Mehran Profile

Mahyar Mehran

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Proceedings Article | 24 March 2015 Paper

Modeling defect tolerance sensitivity to periodic post parameters in microfluidic channels

Mahyar Mehran, Bonnie Gray, Glenn Chapman

Proceedings Volume 9320, 93200B (2015) https://doi.org/10.1117/12.2080870

KEYWORDS: Microfluidics, Particles, Monte Carlo methods, Tolerancing, 3D modeling, MATLAB, Protactinium, Fluid dynamics, Computer simulations, Systems modeling

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Previously we modeled the theoretical benefits of using microfluidic channels that utilize a “Cathedral Chamber” design, in which the ceiling is supported by an array of periodic posts, compared to an array of parallel microfluidic channels. We developed a semi-automated technique that combines a rule-base defect placement system with a 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 rate. Earlier results indicate that Cathedral Chambers, that are supported by an array of 10 by 11 periodic posts with the same size as the spacing have six times higher lifetime expectancy compared to an array of 10 parallel channels, likely due to the provision of multiple paths during localized blockage formation in the Cathedral Chamber. In this paper, we have expanded our investigations by considering the defect tolerance sensitivity to scale by altering parameters such as the number and size of the posts and overall size of the chamber. For one set of simulations, we used the same number of posts in the chamber and the same starting position for the first 10 blockages as in our previous work. However, we shrank the size of the posts to 66% of their former size so that the new channels (flow pathways) are twice the size of the modified posts. In addition, we have also performed initial simulations based on wider microfluidic channels supported by an array of 20 by 11 periodic posts in order to explore their microfluidic behavior and lifetime.

Proceedings Article | 6 March 2014 Paper

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

Mahyar Mehran, Jorden Bryer, Glenn Chapman, Bonnie Gray

Proceedings Volume 8976, 897604 (2014) https://doi.org/10.1117/12.2040612

KEYWORDS: Microfluidics, Particles, Monte Carlo methods, MATLAB, Systems modeling, 3D modeling, Sensors, Statistical analysis, Tolerancing, Statistical modeling

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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.

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