Transcript Slide 1

ME 381R Lecture 21
Introduction to Microfluidic Devices
Dr. Andrew Miner
Nanocoolers, Inc.
Austin, TX 78735
www.nanocoolers.com
[email protected]
Outline
• Microchannels
• Valves
• Pumps
• Microfluidic Thermal Systems
• Sensors
• Extracting, Mixing, Separation, Filtering
Microchannels
• Variety of shapes and manufacturing techniques,
depending on application.
• Typically laminar due to very small length scales
and flow rates. From Evans et al. [2]:
Re D,max 
UDh


10 mms 500m
1
mm
2
s
5
Microchannels
Microchannels
(Garimella and Singhal, Heat Transfer Engineering, 25, p. 15, 2004)
Nu 1.86 RePr
0.33
D L
0.33
f R e 64
f R e 57
0.4
N u d 0.024 R e 0.8
d Pr
f Re
0.182
0.14
Microchannels
(Garimella and Singhal, Heat Transfer Engineering, 25, p. 15, 2004)
h
Nu
d
P const V
1
d2
P const m
1
d2
Passive Valves
Active Valves
• Pneumatic valve:
Pressure pushes
silicone diaphragm
against inlet/outlet.
(Shown closed)
• Thermopneumatic valve:
Bubble pushes silicone
diaphragm against inlet/outlet.
(Shown closed)
Active Valves
• Thermal expansion actuated:
Asymmetric thermal expansion of resistors closes valve boss against outlet.
(Shown open)
Pumps
• Membrane pump:
- Can also be powered by piezoelectric or thermal effects
- Unsteady flow rate
Pumps
• Diffuser pump operation:
- Based on different pressure loss coefficients of
diffuser and nozzle sections
- Powered by membrane
or bubble pumps
- Unsteady flow rate
Pumps
• Bubble pump:
- Typically needs check valve to operate as desired
- Unsteady flow rate
Bubble Jets
(for ink jet printers)
• Bubble pump forcefully ejects ink when expanding
then draws ink from reservoir when collapsing.
High Heat Flux Cooling
Pumps
Classification of Electromagnetic
Pumps (MFD)
After Baker and Tessier, '87
Permanent Magnet, DC
Conduction Pump (DCCP)
Lyon, et. al., '50
High Heat Flux Cooling
Pumps
NC-A, Permanent Magnet Direct
Current Conduction Pump
NC-A
EOP
Centrifugal
Vol
(cm3)
4.4
2
1.5
0.3
31.8
Max. Eff.
(%)
0.5
●
●
R. Drack, '03
S. Yao, et. al., '03
High Heat Flux Cooling
Pumps
Liquid Metal Cooling System
Notebook Computer
High Heat Flux Cooling
Heat Transfer
Theoretical Basis, Laminar and Turbulent Flow in a Tube, Constant
Wall Heat Rate
U
h
q
T w al l T m ean
Laminar Flow
N u d 4.36
q
hd
Turbulent Flow in High and Moderate Pr
Fluids: Dittus-Boelter
N u d 0.024 R e0.8
Pr 0.4
d
Turbulent Flow in Low Pr Fluids: SleicherRouse
N u d 6.3 0.0167 R e0.85
Pr 0.93
d
Pr
Cp
●
●
Re
Ud
G. W. Dittus and L. M. D. Boelter, University of Califronia
Publications in Engineering 2, 443 (1930)
C. A. Sleicher and M. W. Rouse, International Journal of Heat
and Mass Transfer 18, 677 (1975)
High Heat Flux Cooling
Heat Transfer
Turbulent Flow Enhancement of
Heat Transfer
Laminar Flow, All Pr
Radial Diffusive HT, Axial Convective HT
Turbulent Flow, High and Moderate Pr
Radial Convective HT, Axial Convective HT
Turbulent Flow, Low Pr
Radial Diffusive HT, Axial Convection HT
Low Pr Turbulent Flow: Thermally Laminar,
Hydrodynamically Turbulent!!
Microchannel Heat Exchanger Cooling System
(Cooligy)
Cooligy, www.cooligy.com
Sensors
FLOW
• Drag Flow Sensor:
Flow measured by strain
gauge.
• Differential Pressure Flow Sensor:
Flow measured by pressure difference.
PIEZORESISTOR
STRAIN GAUGE
Macro/Micro Mixing Study
(Brenebjerg, et al., 1994 [3])
• In “macro” channels (100 mm long x 300 m wide x 600 m deep):
Good mixing was observed – caused by turbulence from sharp corners.
• In “micro” channels (5 mm long x 180 m wide x 25 m deep):
Very little mixing observed – mixing by diffusion only, with no turbulence.
Diffusion-Based Extractor
• Molecules with large
diffusion coefficients
can be extracted from
those with small
diffusion coefficients.
Active Mixer
(Evans et al., 1997, [2])
• Bubble pumps and one-way bubble
valves mix fluid using chaotic
advection to increase surface area
between mixing fluids.
IN
• Mixing chamber is 600 m wide x
1500 m long x 100 m deep.
• Entire system manufactured on a
single silicon substrate.
OUT
Mixing and Separation
(Lin and Tsai, 2002 [5])
This system mixes two liquids and separates out
any gas bubbles.
Mixing and Filtering
(Lin and Tsai, 2002 [5])
• Mixing effect of bubble
pump cycles (5, 50, 100,
150, 200 Hz, respectively)
• Gas bubble filter – Surface
energy of a gas bubble is less
for a wider channel.
Fluidic Logic
• In 1950’s, there was a push research in this area for control
systems resistant to radiation, temperature, and shock.
• Examples of fluidic logic components:
Microfluidic Logic Integration
(Quake et al., 2002 [7])
• High-density integration of fluidic logic, analogous to electronic ICs.
Microdialysis Microneedle
• Filtering capability built in to
needle wall.
Microneedle Features
• Smallest traditional needles:
- 305 m OD, 153 m ID (30-gauge)
- Only available with straight shafts, no interior features
• Microneedles:
- Almost any size and shape (defined lithographically)
- Can incorporate microfilters for excluding large molecules
- Reduced insertion pain for patient
- Reduced tissue damage
- Capable of targeting a specific insertion depth
- Capable of very low flow rates, but limited in higher flow
rate applications
Hypodermic Injection Microneedles
Device for Continuous Sampling
(Zahn et al., 2001, [6])
• Microdialysis needle filters larger molecules (proteins) to
prevent inaccuracies and reduced sensor life span.
• Sensors and entire fluidic system are located on a single chip.
Three fluids used: 1) sampled fluid from needle, 2) saline to
clean the sensor, and 3) glucose to recalibrate the sensor.
• Device can be worn by patient, and coupled with a similar
device for drug delivery. For example, glucose monitor
coupled with insulin injector for diabetic patients.
• Sensor uses an enzyme to catalyze a reaction with glucose,
resulting in H2O2 oxidizing to a Pt electrode, creating a voltage.
Device for Continuous Sampling
(Zahn et al., 2001, [6])
References
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Kovacs, Gregory T.A., Micromachined Transducers Sourcebook, WCB/McGraw-Hill, 1998.
Evans, J., Liepmann, D., and Pisano, A.P., “Planar Laminar Mixer,” Proceedings of the IEEE 10th
Annual Workshop of MEMS (MEMS ’97), Nagoya, Japan, Jan. 26-30, 1997, pp. 96-101.
Branebjerg, J., Fabius, B., and Gravensen, P., “Application of Miniature Analyzers from Microfluidic
Components to TAS,” van den Berg, A., and Bergveld, P. [eds.], Proceedings of Micro Total
Analysis Systems Conference, Twente, Netherlands, Nov. 21-22, 1994, pp. 141-151.
Not used
Lin, L, and Tsai, J., “Active Microfluidic Mixer and Gas Bubble Filter Driven by Thermal Bubble
Micropump,” Sensors and Actuators, Vol. A 97-98, pp. 665-671, 2002.
Zahn, J.D., Deshmukh, A.A., Papavasiliou, A.P., Pisano, A.P., and Liepmann, D., “An Integrated
Microfluidic Device for the Continuous Sampling and Analysis of Biological Fluids,” Proceedings of
2001 ASME International Mechanical Engineering Congress and Exposition, Nov. 11-16, 2001,
New York, NY.
Quake, S.R., Thorsen, T., Maerkl, S.J., “Microfluidic Large-Scale Integration,” Science, Vol. 298,
pp. 580-584, Oct. 18, 2002.
Intel Corporation, product information from web site (www.intel.com).
Goodson, K.E., 2001, “Two-Phase Microchannel Heat Sinks for an Electrokinetic VLSI Chip
Cooling System,” 17th IEEE SEMI-THER Symposium.
Eksigent Technologies, LLC, information for EK pump from web site (www.eksigent.com).
A. Miner, U. Ghoshal, “Cooling of High Power Density Micro-Devices using
Liquid Metal Coolants," Applied Physics Letters, Vol. 85, pp. 506-508.
Cooligy Inc., www.cooligy.com
Nanocoolers, Inc. www.nanocoolers.com