Date of Graduation

5-2017

Document Type

Thesis

Degree Name

Bachelor of Science in Mechanical Engineering

Degree Level

Undergraduate

Department

Mechanical Engineering

Advisor/Mentor

Tung, Cha-Hung Steve

Committee Member/Reader

Huang, Po-Hao Adam

Committee Member/Second Reader

Kim, Jin-Woo

Abstract

This research focused on the design and testing of a blood-brain barrier (BBB)-on-a-chip microfluidic device produced using 3D printing. First, COMSOL simulations were used to define dimensions of the microchannel that would most accurately replicate the flow environment imposed on the blood-brain barrier, the wall shear stress being the most important characteristic. In using COMSOL, water was used as the simulated fluid and also the testing fluid in the fabricated devices. Therefore, the microsystem is designed to produce the BBB environment using water instead of blood. The numerical simulation parameters were based on theoretical calculations performed to scale up the dimensions of the brain capillary with the BBB to the dimensions of a microchannel that is possible to 3D print. The COMSOL simulation results show that a rectangular channel with a height of 2 mm and width of 0.5 mm will be under a wall shear stress of approximately 0.43 Pa at 2500 μL/min, 0.75 Pa at 4000μL/min, and 1.99 Pa at 9000 μL/min.

A micropump designed and tested by Carlton McMullen is used as the standard for new models, which are fabricated using a MakerBot Replicator 2 3D printer [11]. Its pumping capabilities were tested to determine if it could produce the flow rates found in the numerical simulations. The pump was tested at actuation pressures of 20 psi, 30 psi, and 40 psi, while the actuation frequency was held constant at 10 Hz. The average flow rate was 2810 μL/min at 20 psi, 3420 μL/min at 30 psi, and 5325 μL/min at 40 psi. These results indicate that the current micropump could cause a wall shear stress up to 0.87 Pa in the microchannel where the BBB is replicated and studied. This value is within the range of in vivo shear stress values, validating this method of using water to recreate the environment. With these flow rate results, the micropump design is capable of producing flow rates required for in vivo shear stress values. This research defines 3D printable microchannel dimensions that allow these shear stress values based on attainable flow rates from this micropump.

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