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Monolithic Microfabricated Valves and Pumps by
Multilayer Soft Lithography
EECE 491C
Unger et al. (Quake group, CALTECH)
Science, 2000
How complex and how big?
• ENIAC, first large scale electronic and digital computer
• 30 tons, 19,000 vacuum tubes, 200 kW
• Towards integrated circuits
• Large Scale Integrated Circuits (LSI)
EECE 491C
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Courtesy www-ivs.cs.uni-magdeburg.de
Biochemical Laboratories
• Expensive Reagents• Small amounts of
samples available• High levels of
multiplicity required• Portability• Equipment Costs• Level of training
EECE 491C
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Courtesy www.stanford.edu/group/crg
Courtesy www.nature.com/ vol 442- Yager
Microelectromecanichal structures (MEMS)
• Bulk micromachining:• Single-Crystal silicon
lithographically patterned then etched
• Stress between layers
• Surface Micromachining:• Additive method• Patterning. Max thickness 20 um
• Limited materials• Stiff materials = hard to make
smaller features
EECE 491C
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Courtesy http://dei-s1.dei.uminho.pt
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Courtesy http://www.aero.org
Soft Lithography
EECE 491C
•With only one layer it is difficult to create active devices or moving parts
Multilayer Soft Lithography • Can bond different layers of
elastomer• Elastomer: silicon rubber, 2
component, polymer and cross-linker
• Each layer has excess of one of the 2
• Upon contact layers form hermetic seal
• Can easily create multilayer devices
• Can create electro-magnetic devices by doping
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Valves
• Typical channel size X
• Membrane between layers
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100m
10m
30m
• Response time ~1ms• 1mN of force (100kPa)• Pneumatic activation:
dense packing possible
• Fluid is introduced with pins
• Can accept up to 300 kPa without leakage
Valves and Pressure
• Flow Layer: biological assay, fluid manipulation
• Control Layer: actuate valves• • Valve opening controlled by
fluorescence
EECE 491C
close open
From Valves to Pumps
• A - on/off valve 200x100• B - on/off valve 30x50• C - peristaltic pump• D - grid of valves• E - switching valve• F - section of 7 layer
device• Scale bars: 200 um
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Elastomeric Peristaltic Pump
• 50 kPa of applied pressure
• Channels 100 um wide and 10 um high
• Durable• E coli showed 94%
survival rate
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Valves and Pumps
• Durable• Low dead volumes• Complete sealing even in presence of
particulates• Easy to produce• Cheap• Rapid prototyping• Multiple layers possible• Transparent• Biocompatible• Countless applications
EECE 491C
Courtesy nature.com vol 442 Whitesides, Quake
Valves and Pumps
EECE 491C
Courtesy Carl Hansen
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
Valves and Pumps
EECE 491C
Courtesy Carl Hansen
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
The Multiplexor
• Microvalves are scalable and leakproof
• Can now have multiplexed addressing and control
• Binary tree• fluid channels• control channels• Only 20 control for
1024 flow channels
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2log2 n
n
Memory Storage Design
• 1000 individually addressable 250pL chambers
• Microfluidic memory storage device
• Similar to Random Access Memory (RAM)
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Memory Storage
• Row Multiplexor: fluid trafficking (RAM word line) refreshes compartments within a row
• Column Multiplexor: controls vertical input-output valves for specific central compartments
• Display Monitor
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Microfluidic Comparator Chip
• Allows mixing of 2 separate reagents, unloading
• 256 rxn chambers
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The Experiment
• Ecoli in one compartment• Amplex red (AR) in the other
columnEECE 491C
• Compartments opened• CCP converts AR to resorufin• Control using GFP
Controls
• Heterogeneous mixture of E. coli expressing CCP or eGFP
• Amplified signal dependent only on number of CCP expressing cells in individual chambers
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Conclusions
• Ability to integrate and control many fluidic elements• Selective manipulation and recovery• Scalable devices• Can envision chemical and biochemical analysis• High throughput screening applications, liquid
display technology• Creation of microfluidic LSI• Rapid, simple fabrication• Disadvantages of PDMS
EECE 491C
Critique
• Well presented, ground-breaking• Limited discussion of other techniques available• Weak Biological experiments or applications• Limited discussion of flaws of the materials used
• Certain figures are not very detailed• Would have been interesting to see a picture of the
entire device
EECE 491C
Monolithic Microfabricated Valves and Pumps by Multilayer Soft Lithography