Final Presentation of Microfluidics project

1. Serpent MixerFinal Presentation Group B:WoohyuckChoi

2. Introduction Why is micromixing important? Types of micromixing Principles of micromixing Module 1 (Optimization) Module 2 (Fabrication) Module 3 (Characterization) Comparison to Simulation Type of Mixing Comparison to Other Mixer Conclusions Outline

3. Consumes small amounts of valuable reagents Mixes in relatively short periods of time Applications in: Lab-on-Chip devices DNA sequencing Sample preparation Cell separation and detection Protein folding Why is Micromixing Important? J. Ottino and S. Wiggins, "Designing optimal micromixers," Science (New York, N.Y.), vol. 305, pp. 485, 2004.

4. Active Utilizes disturbances created by external fields Pressure, temperature, electrohydrodynamics, acoustics, electrokinetics etc… Require external power sources (complex integration) Passive Rely totally on channel geometry Simple, low cost, less likely to damage samples Types of Micromixing N. Nguyen T. and Z. Wu, "Micromixers - a review," Journal of Micromechanics, vol. 15, 2005.

5. Molecular Diffusion Increase contact area and decrease diffusion path Parallel lamination Hydrodynamic focusing Chaotic Advection Manipulate the laminar flow across boundary Specific 3-D obstacles needed Principles of Passive Micromixing N. Nguyen T. and Z. Wu, "Micromixers - a review," Journal of Micromechanics, vol. 15, 2005. S. Hardt, K. S. Drese, V. Hessel and F. Schonfeld, "Passive micromixers for applications in the microreactor and μTAS fields," Microfluidics and Nanofluidics, vol. 1, pp. 108-118, 2005.

6. 2-D 3um triangular mesh Values Chosen Variable 1: 40um Variable 2: 30um Variable 3: 30um Module 1 (Optimization) Figure 1. Variables for optimization

7. Simulated in 3-D with 5um triangular mesh. Module 1 (Optimization) 2 Figure 3. σ vs downstream position for simulated channel Figure 4. σ vs Re for simulated channel at 4910um downstream Percent Mixing at 4910um Pressure Drop: Re=.1 99.58% 1.05KPa Re=1 98.40% 10.7KPa Re=10 99.9% 130Kpa

8. SU-8 Master Mold SU-8 2075 spun on clean 3 inch Si Wafer Exposed with I-Line highpass filter 175 mJ/cm2 for 30 sec Oxygen plasma descum PDMS Casting 10:1 elastomer to curing agent mixture Bonding Corona discharge on both PDMS and microscope slide ¼ inch above samples for 20 sec Module 2 (Fabrication)

9. Module 2 (Fabrication) 2 7.387 30.31 40.01 60.38 50.01 33.54 Fig. 5 Critical dimensions of serpent mixer. Table 1. Comparison of expected and fabricated channel dimensions

10. Module 3 (Characterization) Fig 6. Images taken at different positions in channel for Re=1 case.

11. Module 3 (Characterization) 2 Figure 7. σ vs. downstream position for fabricated channel Figure 8. σ vs Re for fabricated channel Table 2. Percent mixing at approximately 1cm downstream

12. Y(90) Position Calculated using a 4th order polynomial fit Re=.1 10895um Re=1 12642um Re=10 10729um Module 3 (Characterization) 3

13. Simulation was rerun for channel with fabricated dimensions. 2-D 2um triangular mesh was used for maximum accuracy Comparison to Simulation Table 3. Comparison of percent mixing at 4910um downstream

14. Primarily diffusive Re=0.1 best mixing Not purely diffusive Re=10 > Re=1 Vorticity present in bends Likely due to race track effect Type of Mixing Figure 9. Vorticity in channel

15. For almost the same Re and Pe values the staggered herringbone mixer achieved σ=.04 (92% Mixing) at 1cm downstream. The Serpent mixer achieved 86.55% mixing ~5% decrease in mixing Comparison to Other Mixer A. D. Stroock, S. K. W. Dertinger, A. Ajdari, I. Mezic, H. A. Stone and G. M. Whitesides, "Chaotic Mixer for Microchannels," Science, vol. 295, pp. 647-651, January 25. 2002.

16. The serpent mixer is a primarily diffusive mixer but due to sharp bends in the channel has some convective behavior. Achieved 86.55% mixing at 1.06cm for Re=0.1 Projected to reach 90% mixing in just over 1cm downstream May reach it sooner but a lot of error in calculations due to low number of data points. Conclusions

17. [1] J. Ottino and S. Wiggins, "Designing optimal micromixers," Science (New York, N.Y.), vol. 305, pp. 485, 2004. [2] N. Nguyen T. and Z. Wu, "Micromixers - a review," Journal of Micromechanics, vol. 15, 2005. [3] S. Hardt, K. S. Drese, V. Hessel and F. Schonfeld, "Passive micromixers for applications in the microreactor and μTAS fields," Microfluidics and Nanofluidics, vol. 1, pp. 108-118, 2005. [4] A. D. Stroock, S. K. W. Dertinger, A. Ajdari, I. Mezic, H. A. Stone and G. M. Whitesides, "Chaotic Mixer for Microchannels," Science, vol. 295, pp. 647-651, January 25. 2002. References

18. Questions ?