Designing and Developing an Active Micromixer Based on Optical Tweezers for Microfluidics

Taheri, Saeed | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47142 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Seyed Reihani, Nader
  7. Abstract:
  8. Microfluidics is a field of science that studies micron-scale characteristics of fluids. In this scale fluids show fascinating behavior far beyond our expectation compared to their large-scale counterparts. One of such peculiar behavior is the mixing of two different liquids flowing inside a microchannel. Due to low Reynolds number, the flow inside such a channel would be dominated by laminar behavior. In this regime mixing of the fluids is only mediated by molecular diffusion which is a rather slow process. In the current thesis, we utilized the rotating ability of optical tweezers to construct an active micromixer for Microfluidics. In order to do this we used birefringent microbeads. The most important achievement of this thesis was considerable enlargement of the visualization field of view while having the bead in trap in order to track the mixing length. In such condition the length of the typical field of view is about 200 micrometers which was extended to about 2 centimeter in this project. All the experiments were carried out inside of a Y-shaped microchannel that were made by PDMS and soft lithographic method. We used a silicon-made mold which provided a channel with squared cross-section with width of 100 micrometers. Particles that were used as micromixers were birefringent vaterite microspheres that also produced at the same laboratory. After crystallization, diameter of the microspheres were about 4-5 micrometers. The trapped particle started to rotate once the polarization state of the laser turned into circular. In order to speed up the mixing process one has to position the rotating bead at the interfacial surface between the two fluids inside the microchannel
  9. Keywords:
  10. Microchannel ; Low Reynolds Number ; Microfluidic Devices ; Microfluidic System ; Optical Tweezer ; Optical Trapping

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