Type of Document Master's Thesis Author Sundaram, Narayan URN etd-12112003-155744 Title Electrokinetically Driven Mixing in a Microchamber for Lab-on-a-Chip Applications Degree Master of Science Department Mechanical Engineering Advisory Committee
Advisor Name Title Tafti, Danesh K. Committee Chair Dancey, Clinton L. Committee Member Saraf, Ravi F. Committee Member Keywords
- Micro-Total-Analysis systems
Date of Defense 2003-11-21 Availability unrestricted AbstractElectrokinetically Driven Mixing in a Microchamber for Lab-on-a-Chip Applications
Micro-Total-Analysis-Systems (μTAS) have been the focus of recent world wide research due to their varied applications. Much of the motivation for the development of μTAS stems from applications in biotechnology and biomedicine. A typical μTAS device includes a number of functional units ranging from sample injection or ingestion, pre-concentration, mixing with reagents, chemical reactions, separation, detection, and possibly a chemical response.
Mixing of constituents is one of the key functions desired of these systems for conducting analyses in a short span of time. The flow regime in these small devices (typical sizes 100μm) being predominantly laminar (Reynolds number, Re < 1), it becomes difficult to rapidly mix the constituent species. Hence for effective mixing, it is necessary to increase the Reynolds number and/or induce bulk motion such that the material interface between the components to be mixed is continuosly augmented.
The method developed to induce such motion is by the application of an AC fluctuating potential field across a microchamber in which mixing is to be performed. The externally applied electric field applies a force on free ions in the charged Debye layer very close to the surface (1-10 nanometers) and induces a flow velocity which is proportional to the electric field. This applied fluctuating electric field gives rise to hydrodynamic instabilities which are responsible for increasing the material contact surface and hence augmenting the rate of mixing by an order of magnitude or more over pure diffusion.
To further enhance mixing, microbaffles are strategically placed inside the microchamber and the mixing time was further decreased by a factor of two. Mixing was also studied in a neutral (no charge on the walls) microchamber. It was found that the mixing achieved in the absence of surface charge was comparable to the mixing achieved in the case with microbaffles.
This work establishes that CFD is a useful tool that is capable of providing insight into the flow physics in devices with very small length scales.
Filename Size Approximate Download Time (Hours:Minutes:Seconds)
28.8 Modem 56K Modem ISDN (64 Kb) ISDN (128 Kb) Higher-speed Access Thesis-Sundar.pdf 4.88 Mb 00:22:35 00:11:36 00:10:09 00:05:04 00:00:26
If you have questions or technical problems, please Contact DLA.