Designing a Microfluidic Device with Nutrient Gradient
Date Issued
2016
Date
2016
Author(s)
Lin, Hung-Yi
Abstract
This study focuses on designing a microfluidic device to generate nutrient gradient for the study of plankton in chemotaxis in the future. The PDMS microfluidic platform is consisted of three layers: the gradient channel, the porous membrane, and the microcavity channel. The 3 layer structure is aimed at generating concentration variation in the microcavity by reducing the influence from the flow field of the gradient channel. The micro cavity channel has a circular pocket connected to a straight channel. The gradient channel has two symmetrical channels, one for water and the other for the dye solution. By transport through the perforated membrane, concentration gradient is formed in the microcavity. The alignment of the gradient channel and the microcavity channel of the bottom layer can be changed to alter the concentration gradient is formed in the microcavity. In addition, we design membrane with different pore size and pitch to study their effect on the concentration distribution in the microcavity. The result shows that varying the flow velocity of the microcavity channel is the easiest way to change the concentration field. When velocity increases, the average concentration in the microcavity decreases, without significant change of its distribution. In addition, The direction of the concentration gradient can be easily change by the orientation between the gradient and the microcavity channels. When the gradient channel is aligned parallelly to the straight channel of the microcavity layer, higher concentration is found in the bottom of the pocket. When the gradient channel is aligned perpendicularly to the straight channel of the microcavity layer, higher concentration is found near the left edge of the microcavity. For the counterflow configuration in the gradient channel, the concentration is not affected by the flow in the microcavity channel. When the membrane has more pores, porosity too large such that the flow in the microcavity channel may interfere the flow in the gradient channel, which makes the dye more difficult to pass through the pores. Therefore, membrane with large porosity is not recommended. Yet, lager pore size lead to higher concentration gradient in the cavity and the pick value can reach as higher as 1500 m-1. In this study, we successfully manipulate the concentration field in the microcavity by varying the flow field in the gradient channel and the microcavity channel. To reduce the effect of flow field on the concentration distribution, membrane with lower porosity is preferred.
Subjects
microfluidic device
concentration gradient
porous PDMS membrane
PVA membrane
manipulative microhabitat
chemotaxis
Type
thesis
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