Micro MixersMicro Mixers
ME 595ME 595Special Topics in Mechanical Engineering – Micro FluidicsSpecial Topics in Mechanical Engineering – Micro Fluidics
Western Michigan UniversityWestern Michigan University
Presented by:
John TomasiNovember 30th, 2004
Presentation for:
Dr. Liou’s ME 595/695 class
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Macroscopically, mixing is usually Macroscopically, mixing is usually accomplished through turbulenceaccomplished through turbulence
II. Introduction to Mixing. Introduction to Mixing
transverse velocity componentstransverse velocity components
spontaneous flow fluctuationsspontaneous flow fluctuations folding and stretching of fluid particlesfolding and stretching of fluid particles
Chaotic behavior that randomly redposits Chaotic behavior that randomly redposits particles until homogeneity is achievedparticles until homogeneity is achieved
An everyday occurrence that is An everyday occurrence that is usually taken for grantedusually taken for granted
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Microscopically, turbulence is difficult Microscopically, turbulence is difficult to achieveto achieve
II. Introduction to Mixing. Introduction to Mixing
reduced length scale results in low reduced length scale results in low Re and highly Re and highly laminarlaminar flows flows
fluids tend to move in layersfluids tend to move in layers mixing is achieved solely through mixing is achieved solely through
diffusion along the fluid-fluid boundarydiffusion along the fluid-fluid boundary
Dl
mixt 2
2lPey DUlPe
slow and/or lengthy processslow and/or lengthy process PPééclet Number is ~ 100, clet Number is ~ 100,
Micro MixersMicro Mixers J. TomasiJ. Tomasi
IIII. Importance of Mixing. Importance of Mixing
Sample AnalyzingSample Analyzing
Chemical Reaction KinematicsChemical Reaction Kinematics
Drug/Sample DeliveryDrug/Sample Delivery
proteinsproteins DNADNA
Additional laboratory procedures necessary Additional laboratory procedures necessary for a laboratory to fit on a “chip”for a laboratory to fit on a “chip”
Micro MixersMicro Mixers J. TomasiJ. Tomasi
ActiveActive
IIIIII. Types of Mixers. Types of Mixers
All micro mixing devices and techniques All micro mixing devices and techniques that utilize devices separate from the that utilize devices separate from the flow channel to induce mixing.flow channel to induce mixing.
All micro mixing devices and All micro mixing devices and techniques that operate independent techniques that operate independent of external intervention.of external intervention.
PassivePassive
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Electro-osmosis with AC current appliedElectro-osmosis with AC current applied
IVIV. Active Mixers. Active Mixers
mixing occurs at particular frequenciesmixing occurs at particular frequencies
operation credited to instability that operation credited to instability that develops at particular frequenciesdevelops at particular frequencies
experimentally shown to reduce mixing experimentally shown to reduce mixing time from 500 sec. to as low as 3 sec.time from 500 sec. to as low as 3 sec.
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Electro-osmosis with AC current appliedElectro-osmosis with AC current applied
IVIV. Active Mixers. Active Mixers
• Advantages:Advantages:
◦ requires high voltagerequires high voltage
• Disadvantages:Disadvantages:
◦ utilizes common microfluidics deviceutilizes common microfluidics device
◦ sensitive to contaminates in the systemsensitive to contaminates in the system
◦ only low flow rates createdonly low flow rates created
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Orthogonal PerturbationsOrthogonal Perturbations
IVIV. Active Mixers. Active Mixers
transverse velocity components transverse velocity components artificially created by periodic injectionsartificially created by periodic injections
cross-flow establishes folding of fluid layerscross-flow establishes folding of fluid layers
operates best with particular operates best with particular injection frequenciesinjection frequencies
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Orthogonal PerturbationsOrthogonal Perturbations
IVIV. Active Mixers. Active Mixers
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Electrowetting-On-Dielectric (EWOD)Electrowetting-On-Dielectric (EWOD)
IVIV. Active Mixers. Active Mixers
droplet baseddroplet based• sandwiched bi-fluid droplet sandwiched bi-fluid droplet
with only two sides of contactwith only two sides of contact
matrix of electrically charged plates matrix of electrically charged plates direct droplet to roll in a box patterndirect droplet to roll in a box pattern
each complete roll increases the number each complete roll increases the number of fluid interfaces exponentially (2of fluid interfaces exponentially (2nn))
• BC’s allow fluid layers to fold BC’s allow fluid layers to fold as droplet movesas droplet moves
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Electrowetting-On-Dielectric (EWOD)Electrowetting-On-Dielectric (EWOD)
IVIV. Active Mixers. Active Mixers
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Electrowetting-On-Dielectric (EWOD)Electrowetting-On-Dielectric (EWOD)
IVIV. Active Mixers. Active Mixers
• Advantages:Advantages:
◦ complex constructioncomplex construction
• Disadvantages:Disadvantages:
◦ requires only 30 Vrequires only 30 Vrmsrms
◦ small throughputsmall throughput
◦ experimentally shown to reduce experimentally shown to reduce mixing times by as much as 50xmixing times by as much as 50x
◦ compactcompact
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Serpentine and Helical ChannelSerpentine and Helical Channel
VV. Passive Mixers. Passive Mixers
fluids mix while the follow a winding fluids mix while the follow a winding pathpath
• operating principle: chaotic advectionoperating principle: chaotic advection
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Serpentine and Helical ChannelSerpentine and Helical Channel
VV. Passive Mixers. Passive Mixers
• Advantages:Advantages:
◦ effective in flows with Re > 1effective in flows with Re > 1
• Disadvantages:Disadvantages:
◦ compactly places long channel required compactly places long channel required for diffusive mixing on a microdevicefor diffusive mixing on a microdevice
◦ helical channel extremely difficult helical channel extremely difficult to constructto construct
◦ no great reductions in mixing timesno great reductions in mixing times
◦ very simple to operatevery simple to operate
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Staggered Herringbone Mixer (SHM)Staggered Herringbone Mixer (SHM)
VV. Passive Mixers. Passive Mixers
raised ridges on the channel floor cause raised ridges on the channel floor cause the fluids to rotate within the channelthe fluids to rotate within the channel
• increases contact area and increases contact area and induces layer foldinginduces layer folding
various configurations of ridgesvarious configurations of ridges
Requires ridge heights of only 20 -Requires ridge heights of only 20 -30 % of mean channel height30 % of mean channel height
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Staggered Herringbone Mixer (SHM)Staggered Herringbone Mixer (SHM)
VV. Passive Mixers. Passive Mixers
• Advantages:Advantages:
◦ superiority to regular channels superiority to regular channels increases with flow velocityincreases with flow velocity
◦ requires only one additional step requires only one additional step during the construction phase over during the construction phase over regular channelsregular channels
◦ 1cm/s flow in 1001cm/s flow in 100μμm square channel requires 100cm for m square channel requires 100cm for diffusion alone, but only 1 cm with SHMdiffusion alone, but only 1 cm with SHM
◦ functions independent of Re for Re<100functions independent of Re for Re<100
◦ same fluid in the same channels flowing at 10cm/s would same fluid in the same channels flowing at 10cm/s would require 1,000cm for diffusion, but only 1.5 cm for SHMrequire 1,000cm for diffusion, but only 1.5 cm for SHM
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Hydrodynamic FocusingHydrodynamic Focusing
VV. Passive Mixers. Passive Mixers
achieves mixing by reducing the achieves mixing by reducing the layer thickness over which diffusion layer thickness over which diffusion must operatemust operate
◦ the thickness of each layer the thickness of each layer is controlled by its injection is controlled by its injection raterate
utilizes a microjet and two side channels to utilizes a microjet and two side channels to create three thin fluid layerscreate three thin fluid layers
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Hydrodynamic FocusingHydrodynamic Focusing
VV. Passive Mixers. Passive Mixers
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Hydrodynamic FocusingHydrodynamic Focusing
VV. Passive Mixers. Passive Mixers
• Advantages:Advantages:
◦ best suited for reaction kinematics best suited for reaction kinematics investigationsinvestigations
• Disadvantages:Disadvantages:
◦ extremely quick mixing times – as extremely quick mixing times – as low as 10 and 20 low as 10 and 20 μμss
◦ small volume consumption ~ 5nsmall volume consumption ~ 5nll/s/s
◦ properties of system well understoodproperties of system well understood
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Droplet Based Recirculating FlowDroplet Based Recirculating Flow
VV. Passive Mixers. Passive Mixers
recirculating flow within droplet folds fluid recirculating flow within droplet folds fluid layers into one anotherlayers into one another
• requires that “channel fluid” and droplet requires that “channel fluid” and droplet fluid be immisciblefluid be immiscible
• ““twirling” of droplet tip initiates mixingtwirling” of droplet tip initiates mixing
• surface tension between water and “channel surface tension between water and “channel fluid” must be greater than between water fluid” must be greater than between water and droplet fluidsand droplet fluids
droplet length controlled by relative injection droplet length controlled by relative injection raterate
fluids to be mixed and water are injected into a fluids to be mixed and water are injected into a stream of fluid moving through a microchannelstream of fluid moving through a microchannel
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Droplet Based Recirculating FlowDroplet Based Recirculating Flow
VV. Passive Mixers. Passive Mixers
Micro MixersMicro Mixers J. TomasiJ. Tomasi
Droplet Based Recirculating FlowDroplet Based Recirculating Flow
VV. Passive Mixers. Passive Mixers
• Advantages:Advantages:
◦ restrictive on fluid combinationsrestrictive on fluid combinations
• Disadvantages:Disadvantages:
◦ quick mixing times ~ as low as 25 quick mixing times ~ as low as 25 μμss
◦ droplet length needs to be within a droplet length needs to be within a specific range for efficient mixingspecific range for efficient mixing
Micro MixersMicro Mixers J. TomasiJ. Tomasi
ThankThank You Youfor listeningfor listening
Questions?Questions?ThankThank You You