A novel mathematical approach that simplifies micro fluidic serial dilution based-gradient generators and controls the concentration gradient and flow rates within microsystems has been developed. This approach may be used to produce precise outlet profiles; linear, nonlinear and arbitrary concentration gradients can be generated. Four microreactor designs have been modelled and studied comprehensively to produce linear outlet concentration gradients with equal outlet flow rates, with the potential for high throughput applications that could span a wide range of chemical and biological studies. Two designs of two-inlet six-outlet (2-6) networks and another two designs of two-inlet eleven-outlet (2-11) network designs were introduced. The (2-6) network designs produce a linear outlet concentration gradient of 0, 20, 40, 60, 80 and 100% while the (2-11) network designs produce a more precise linear outlet concentration gradient with 10% increments. The mathematical study involves 1) analytical modelling of the performance of the networks with dilute inlets of amaranth solutions and water, 2) optimisation of the channel geometry and 3) numerical simulations for the entire fluid dynamic characteristics. Experimental validation for the mathematical models was carried out on three fabricated micro reactors, using a purpose built integrated optical instrument. The performance of the designs was investigated at different inlet flow rates of 0.1-1 Jllls per inlet for the (2-6) network designs and 0.1-3.2 Jllls per inlet with the (2-11) network devices. Good agreement between the experimental investigations and the mathematical predictions was found overall. Precise linear concentration gradients were found, with R2 = 0.9973 and 0.9991 for the (2-6) designs at 0.1 Jllls per inlet and R2 = 0.9992 for the (2-11) designs at 0.8 Jllls per inlet. Mathematic~l modelling to study the performance of the networks with viscous inlets was also undertaken. The performance of the first (2-6) network design was fully characterised at inlet viscosity ratios of up to about 4:1. This study was evaluated experimentally using different concentrations of sucrose (0.1-1.5 mollkg) and glycerol splution (10-40 wt%), with inlet flow rates of 0.5-5 Jllls per inlet. Good agreement between the mathematical model and the experimental r~sults was found at optimised inlet flow rates. 'S' shaped profiles were found for the outlet gradient at higher inlet viscosity ratios. The generation of pH gradients within the networks was also studied mathematically, and experimental investigations were carried out using fluorescence (ietection with a pH sensitive fluorescent dye. The design was shown to be suitable for pH gradient generation, which could be -applicable for isoelectrophoretic focusing separations.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:505412 |
| Date | January 2009 |
| Creators | Yusuf, Hayat Abdulla |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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