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© 2006 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary
CFD for MicrofluidicsCFD for Microfluidics
Application Examples Fluent
Ralf Kröger, [email protected] Deutschland GmbH
Application Examples Fluent
Ralf Kröger, [email protected] Deutschland GmbH
© 2006 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary
Examples on what we have simualted in microfluidics
• Fluid transport mechanisms
• Drop forming (emulsions)
• Macroscopic Particle Model (MPM)
• Mixing mechanisms
ContentContent
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• Advantages:
– Small sample volumes– Decreased analysis times– Readily automated– Parallelizable– Portable– Low materials cost
• Challenges
– Minimize dispersion– Enhance mixing– Integration/Packaging
Why microfluidics ?Why microfluidics ?
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• Applications:
– Biological/chemical agent detection– Drug discovery (high-throughput screening)– Point-of-care diagnostics– DNA sequencing– Drug delivery– Lab on a chip– Diagnostic equipment– Micro-reactors– Ink jet printing– Fuel cells Quantitative gene expression results using a Polymerase
chain reaction, Applied Biosystems
Industries:FoodPharmaCosmeticsMedicineBiotechnology
Microfluidic TechnologyMicrofluidic Technology
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• Transport of fluids and species and cells
• Droplet creation and breakup
• Mixing and Dispersion
• Reactions
Design concerns in
microfluidic devices
Design concerns in
microfluidic devices
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• “Neutral” hydrodynamics (NHD)
• pressure• centrifugal forces• surface tension
• Electrohydrodynamics (EHD)
• electrophoresis• electro-osmosis• isotachophoresis
Transport mechanismsTransport mechanisms
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• Pumps use a combination of nozzles and a membrane diaphragm or piezo-elements to operate
• FSI applications
Pressure Driven: Micro PumpsPressure Driven: Micro Pumps
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Surface Tension Driven FlowsSurface Tension Driven Flows
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Wetting angle 45° Fluent Modul VOF
small channel height 0.25 mm small channel height1 mm
Surface Tension Driven Flow:
Capillary Stops
Surface Tension Driven Flow:
Capillary Stops
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Wetting angle 70° Fluent Modul VOF
Pressure Driven Flow:
With surface tension effects
Pressure Driven Flow:
With surface tension effects
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Fully Wetting Fluent Modul VOF
Pressure Driven Flow:
With surface tension effects
Pressure Driven Flow:
With surface tension effects
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• Need to produce mono-dispersed droplets of defined sizefor various emulsification processes and for metering varying volumes of chemical samples.
• process variables are easy to manipulate
Droplet generationDroplet generation
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• Emulsions formed because droplets were pinched off by the flow fluid
• size of the droplet controlled by velocity of the water and oil
• wall surface must be hydrophobic– If wall surface is hydrophilic stratified flow resulted
Micro T junction:
Water in oil emulsions
Micro T junction:
Water in oil emulsions
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• Hydrophobic wall
• Hydrophilic wall
Red – OilBlue – Water
Micro T junction:
Water in oil emulsions
Micro T junction:
Water in oil emulsions
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Thanks to Mark Kielpinski
Institut für Physikalische Hochtechnologie e.V. Jena BMBFFörderkennzeichen 16SV1998
Micro T junction:
Water in oil emulsions
Micro T junction:
Water in oil emulsions
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• Link et al., Geometrically mediated breakup of drops in microfluidic devices, PRL, Feb 2004, proposed the use of T junctions with differently sized arms to generate a controlled poly-disperse emulsion
Micro T junction: Emulsions with
defined Particle Size Distribution
Micro T junction: Emulsions with
defined Particle Size Distribution
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Fluent simulations
Video from experiments
http://focus.aps.org/story/v13/st4
Micro T junction:
Symmetric breakup
Micro T junction:
Symmetric breakup
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• Ratio of the length of the arms: 1:5.2• Ratio of the size of droplets: 5.2:1 (Experimental)• Ratio of the size of droplets: 5.4:1 (Fluent predictions)
Micro T junction:
Non-Symmetric breakup
Micro T junction:
Non-Symmetric breakup
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Micro T junction:
Cascading Drop Production
Micro T junction:
Cascading Drop Production
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Micro T junction:
Drop–Channel–Ratio is important
Micro T junction:
Drop–Channel–Ratio is important
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Y-JunctionY-Junction
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Application: Ink JetApplication: Ink Jet
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Macroscopic Particle ModelMacroscopic Particle Model
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Macroscopic Particle ModelMacroscopic Particle Model
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Macroscopic Particle ModelMacroscopic Particle Model
Particle
Particle Velocity
Touched Cells
Fluid Cells
Particle Velocity imposed on touched cells
Fluid Velocity
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• Major problem with micro scale is lack of turbulence• Mixers cannot use impellors• Diffusion mixing is dominant• Contact time is limited by device dimensions• Mixer types
– Static mixers• Vortex mixer• T/Y-joints• U-tube configuration
– Dynamic mixers• Oscillating jet
– Mixing in drops
MixersMixers
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• Diffusion coefficient - 1e-9
• Diffusion coefficient - 1e-10
– (typical miscible liquids)
• Diffusion coefficient - 1e-11
Diffusion EffectsDiffusion Effects
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• Continuous jets set up an oscillating flow• Mixed product removed from both outlets• Larger contact area between reagent streams then for co-flow system
Oscillating jet mixerOscillating jet mixer
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Mixing by secondary flowsMixing by secondary flows
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Institut für Physikalische Hochtechnologie e.V. Jena BMBFFörderkennzeichen 16SV1998
Injection adding and mixing by Injection adding and mixing by Injection adding and mixing by Injection adding and mixing by
secondary flow in drops in channelssecondary flow in drops in channelssecondary flow in drops in channelssecondary flow in drops in channels
Injection adding and mixing by Injection adding and mixing by Injection adding and mixing by Injection adding and mixing by
secondary flow in drops in channelssecondary flow in drops in channelssecondary flow in drops in channelssecondary flow in drops in channels
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Institut für Physikalische Hochtechnologie e.V. Jena BMBFFörderkennzeichen 16SV1998
Simulation of Injection addingSimulation of Injection adding
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Institut für Physikalische Hochtechnologie e.V. Jena BMBFFörderkennzeichen 16SV1998
Mixing Drop in channel: PIV resultsMixing Drop in channel: PIV results
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in the drop reference frame wall moves to the left
drop moves to the right (2D-simulation)
Mixing vortices within moving long dropMixing vortices within moving long drop
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Institut für Physikalische Hochtechnologie e.V. Jena BMBFFörderkennzeichen 16SV1998
Mixing Drop in bending channel
PIV results
Mixing Drop in bending channel
PIV results
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Two fluids
2D rotation around centerOnly wall effects
Mixing in rotating compartmentsMixing in rotating compartments
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lab reference frame
2D rotation around center
Mixing in rotating compartmentsMixing in rotating compartments
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moving reference frame
2D rotation around center
Mixing in rotating compartmentsMixing in rotating compartments
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2D rotation off center
Mixing in rotating compartmentsMixing in rotating compartments
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2D rotation off center
moving reference frame
Mixing in rotating compartmentsMixing in rotating compartments
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Top light fluid (900 kg/m^3)Bottom heavy fluid (1000 kg/m^3)
2D rotation off centerWall and gravity effects
Gravity
Mixing in rotating compartmentsMixing in rotating compartments
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Interestingmixing plane
2D rotation off centerWall and gravity effects
Mixing in rotating compartmentsMixing in rotating compartments
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• CFD gives ‘perfect’ simulation• Much quicker to model multiple geometries• All information obtained, not just at selective
datum points• Easy interpretation of results• May need some validation to prove results
DiscussionDiscussion
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Thanks a lot for Your attention !
Thanks to
Rob Woolhouse, Fluent Europe Ltd, UKMarc Horner, Fluent Evanston, USASrinivasa Mohan, Fluent India
Mark Kielpinski, Institut für Physikalische Hochtechnologie e.V. Jena
Thank You !Thank You !
Ralf Kröger, Fluent Deutschland GmbH, [email protected]