Advances in microfluidics have led to the development of devices which can perform simple operations on fluids with the aim of developing a fully integrated "lab-on-a-chip". Of prime importance to this procedure is the efficient operation of each individual component. Using theoretical prediction sand two-dimensional Molecular Dynamics (MD) simulations, we have explored the operation of two such devices: one which forces a cavity of fluid into rotational motion and one to mix two different fluid species. For the rotational operation, we have referred to experimental results for a circular cavity coupled to a microfluidic channel in which a laminar flow is induced. This flow causes the fluid in the cavity to rotate which we model with MD simulations. We examine the role of wall-fluid interactions and its effect on enhancing the amount of angular momentum generated in the cavity. The reduction in wall-fluid interaction allows the fluid to slip along the wall and acquire a greater level of spin. We hope this technique can be applied experimentally to enhance the rotation in these devices. For the mixing operation, we examined a previously studied theoretical system where the authors claim obstacles in microchannels increase mixing efficiency for a fluid composed of two species. We make theoretical predictions to the contrary and demonstrate, using MD simulations, that our predictions are correct. Our results show that obstacles have two effects. First, obstacles increase the amount of contact between fluid species which only has a negligible effect on increasing the mixing efficiency. Second, the obstacles flatten the normally Poiseuille (quadratic) flow profile over a finite channel length which decreases the distance required for partial but not complete mixing. We demonstrate that all channels of at least a certain length, defined by the diffusive properties of the channel, will reach full mixing at the same point. Both projects illustrate the utility of MD simulations in predicting fluid behaviour in microfluidic systems. Our aim is that these studies can be integrated into the greater body of knowledge pertaining to microfluidics.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/27400 |
| Date | January 2006 |
| Creators | Oliver, Eric C. J |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 79 p. |
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