Axel Guenther

1
Multiphase Microfluidics Flow, Dispersion and
Nanomaterial Synthesis
Coding and Computation in Microfluidics May 24,
2007 MIT
Acknowledgements Klavs F. Jensen, Martin A.
Schmidt, Moungi G. Bawendi, (MIT), Saif A. Khan
(NUS), Michiel Kreutzer (TU Delft), Brian K. Yen
(Caltech)
Axel Guenther Department of Mechanical and
Industrial Engineering Institute of Biomaterials
and Biomedical Engineering University of Toronto
2
Flows, Transport and Chemical Reaction
Günther et al. (2006) Lab on a Chip 6
3
Gas-Liquid Flow Regimes
Günther et al. (2006) Lab on a Chip 6
4
Segmented Flow
Günther et al. (2006) Lab on a Chip 6
5
Reducing Complexity Phase Separation
Günther et al. (2006) Lab on a Chip 6
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Microfluidics-Enabled Strategies to Form Materials

• Scalable multiphase
• Platforms for nanomaterial
• synthesis and cell biology

Characterization Imaging, Integrated sensors
Flow and transport fundamentals
de Mas, Guenther et al. (2003)
Nanomaterial Synthesis
Guenther et al. (2004,5)
Stroh et al. (2005) Yen et al. (2005)
7
Reduced Sample Dispersion in Segmented Flow
Analysis
8
Chemical Reactions in Multiphase Microsystems
9
Building Systems
10
Building Systems
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Example Particle Synthesis (Example Colloidal
Silica)
Laminar flow
37

• Single phase laminar flow ?wide particle size
  distribution

Segmented Flow
11
Segmented G-L flow ? narrow size distributions
(comparable to batch)
Guenther, Khan, et al. (2004) Lap on Chip 4
Khan, Guenther, et al. (2004) Langmuir 20
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Application Controlled Synthesis of CdSe Quantum
Dots

• Colloidal semiconductor quantum dots (QDs) have
  been extensively studied for use in a variety of
  optical applications.
• QDs (2-10 nm diameter) consist of a semiconductor
  core surrounded by a layer of organic caps.
• Properties are size-dependent
• Emission can be tuned over (most of) the visible
  spectrum
• QDs can have high quantum yields and narrow
  emission profiles)

Stroh et al. (2005) Nature Medicine 11(6)
2 nm
10 nm
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Microfluidic Chip Fabrication
Draw-out channel 50mm deep
6 in. Si wafer capped with pyrex
Initial meandering section

• Temperature and chemical resistance
• Reduced thermal stresses

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Integrated Microfluidic Platform for Quantum Dot
Synthesis in Segmented Flow
QD fluorescence
lt80C
Outflow
260C
Flow
Reactor under UV illumination
Inflow
1 mm
G 60µL/min, L 30µL/min

• Slugs are very uniform
• Reaction and quench regions are thermally isolated

Yen, Guenther, et al. (2005) Angew. Chemie Int.
Ed. 44(34)
15
Microfluidic Synthesis in Single vs Multiphase
Flow
size

• Size distribution (indicated by PL FWHM) is
  greatly improved in the segmented flow case ?
  QDs of excellent quality obtained!
• For the single phase case, the size distribution
  broadens at shorter times while for the segmented
  flow case, FWHM remains narrow over entire range
  of reaction times.

Yen, Guenther, et al. (2005) Angew. Chemie Int.
Ed. 44(34)
16
Integrated Microfluidic Platforms
Controlled high-temperature synthesis
World-to-chip Interconnects High-pressure,
high-temperature
Microfluidic Silicon-glass chip
300C, up to 80 bar
Analysis
Hrs-day
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Summary

• Unique flow and transport processes of multiphase
  microsystems (segmentation, mixing, dispersion,
  separation)
• Integration Combine multiphase blocks, Key
  Tools that reduce complexity!
• Silicon/glass-based platform for high-temperature
  synthesis for wide range of nanomaterials
• Rich non-linear behavior at unconventional
  conditions

18
Acknowledgements

• Martin A. Schmidt, Howard A. Stone
• Jensen Research group
• MIT MicroChemical Systems Technology Center
• Microsystems Technology Laboratories (MTL) MIT