Microfluidics: Mathematical Modeling and Empirical Analysis of the Burst Frequencies of a Novel Fishbone Capillary Valve and the Development of an Algorithm to Calculate its Theoretical Hold Time
Advisor:Lee, L. James
Fishbone Capillary Valve
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Chemical and Biomolecular Engineering Honors Theses; 2006
A highly integrated microfluidic compact-disk (CD) platform is being developed by Lee et al. The device is a polymer CD that contains fabricated arrays of microfluidic systems on its surface. This microfluidic CD platform is used in conjunction with a separate electronic unit that controls the spinning velocity of the disk and contains the appropriate biosensors for data acquisition. Centrifugal forces pump the liquid through the microchannels and passive capillary valves are used to gate fluid flow. This biomedical microdevice can be used as an integrated and portable high-throughput screening tool for enzyme linked immunosorbent assay (ELISA), clinical diagnostics, drug discovery, microreaction technology, bioseparations, etc. In order for the device to function properly, precise control of the flow sequencing must be maintained. If the working fluid is a protein or biological solution, then protein adsorption on the channel wall can change surface properties of the polymer over time. These changes in surface properties can cause the passive capillary valve to fail and disrupt proper flow sequencing within the microfluidic device. A novel “fishbone” capillary valve has been developed that seeks to overcome these problems. This valve contains a series of capillary valves arranged in the shape of a fishbone. The capillary fishbone valve must have the desired burst frequencies and a sufficient hold time in order to precisely control the flow of protein and biological fluids. In order to properly design this valve, one must have a thorough quantitative understanding of how key parameters impact the burst frequency and hold time of a fishbone. Rigorous theory and mathematical modeling have been applied to these problems to achieve this understanding. The governing equations have been derived to quantitatively calculate the burst frequencies and hold time of a capillary fishbone valve. Specifically, the general equation for the burst frequency of the nth fishbone within a capillary fishbone valve has been derived. Also, an algorithm has been developed to calculate the theoretical hold time of a capillary fishbone valve. Two user-friendly MATLAB computer programs have been written to calculate both the burst frequency of the nth fishbone and the theoretical fishbone hold time in response to key input parameters. The theory, mathematical models, algorithms, and computer programs explained in this thesis are powerful design tools for the next generation microfluidic CD platform.
Nanoscale Science and Engineering Center
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