Class 7 Microfluidic Platforms
Compared, Winter 2011
Content
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Fluidics Applications
Scaling in Fluidics
A CD as a Fluidic Platform
Nanofluidics
Challenges in Microfluidic Platforms
Fluidics Applications
Memory devices today
and tomorrow
Diagnostics/Molecular
diagnostics today and
tomorrow
DNA
RNA
bacteria,
cancer cell,
WBC, et al
Raw sample
Cell
Separation
Hybridization
Electrophoresis
Sequencing
protein
Cell Lysis,
Purification
Sample Preparation
Amplification
Fluidics Applications

Lab-on-a-chip:
– One system to provide all of the
possible required analyses for a
given type of problem
– All
processing
steps
are
performed on the “chip”
– No user interaction required
except for initialization
– High throughput screening (HTS)
and diagnostics are two major
applications for Lab-on-a-chip
– Partitioning of functions between
disposable and instrument is very
different for HTS and Molecular
PROPULSION
Diagnostics
Mechanical pressure
Acoustic
Centrifugal
Instrument
Power
Propulsion
Heater (PCR)
Electronics
Detection
Disposable
Cassette
Reagents
Fluidics
Electrokinetic
Fluidics Applications
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Lab-on-a-chip:
– Goals
» Portable
» Robust
» Easy to use
» Flexible
» Inexpensive
» Modular?
– Components:
» Separation
» Mixing
» Reaction(s)
» Sample injection
» Sample preparation
» Detection
» Pumping
» Transport (channels)
» Reservoirs
» Flow control
» Intelligence and Memory
» Power
» Display
Scaling in Fluidics
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Most sensing techniques scale poorly in the
micro domain (-)
Often large samples are required to get
enough target species collected (-)
Short analysis time dictates small devices
(+)
Fast heating/cooling (e.g., for PCR) requires
small samples (+)
All flow is laminar (little turbulent mixing) (for mixing)
Surface tension becomes significant (+/-)
No inertia effects (+/-)
Apparent viscosity increases (+/-)
Evaporation is very fast for small samples (-)
Devices are almost always too large for Si to
be a solution.
Different Propulsion Options-Pumps

Propulsion Mechanisms-Pumps:
– Mechanical
(pneumatic/hydraulic)-example shown on the right is
the
blister
pouch
(kodak/Johnson&Johnson)
– Electrokinetic
– Thermal (shape memory alloy,
phase changes)
– Acoustic
– Centrifuge
– Electrohydrodynamic
– Magnetic
– Chemical (hydrogel, osmotic
pressure, phase change)
– Electrochemical (create bubles
through electrolysis)
Different Propulsion Options

Mechanical (blister pouch for
example)
– Scales as L3
– No fluid contact
– Generic
– Innovation in the blister
pouch
– Solves liquid and vapor
valving !!
– Difficult
to
further
miniaturize
– Difficult to multiplex
Different Propulsion Options
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Electrokinetic
osmosis):
(electro-
– Requires
materials
with
surface charge
– Preferably permanent
– Glasses and many polymers
have permanent negative
surface charge
– Positive charges assemble
on surface
– Applied charges pull
assembled charges
– Charges at surfaces drag
bulk material
– Plug flow
Different Propulsion Options
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Electrokinetic (DC)
– High voltage source is not
convenient
– Many parameters influence
propulsion force
– Not generic
– Mixing difficult to implement
– Fluid contact
– Scales as L2
– First products (Caliper)
– May solve liquid valving but not
for vapors !
– Better for high-throughput
screening (HTS) and smaller
samples
Different Propulsion Options
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Centrifugal
– Compatible with a wide range of
samples
– Mixing easy to implement
– Sample preparation easier
– Simple and inexpensive CD
player for drive
– No fluid contact
– Established
– Generic
– Solves liquid valving elegantly
– Scales a bit better than l3
– Most functions demonstrated
– Cell work easier
– Better for diagnostics
Different Propulsion Options
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Acoustic (Dick White’s flexural
plate wave device for example)
– Scales as L2
– No fluidic contact
– R & D phase
– Generic
– Doesn’t solve valving yet
– ZnO technology still difficult
to reproduce
– Easy to further miniaturize
A CD as a Fluidic Platform
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Why a CD as a Microfluidic Platform ?
– Microscope, smart centrifuge and plastic
disposable with fluid storage capability
– Comparison with other microfluidic
platforms
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Example Applications
Most Recent Application: Integrated
Molecular Diagnostics (DNA Arrays on a
CD)
– Lysis
» Lysis 1: multiplex
» Lysis 2: single circular
– Fast hybridization detection
» Optical
– This is where we are headed
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Conclusions
A CD as a Fluidic Platform
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The optical disc drive is a
sophisticated laser scanning
microscope
designed
to
characterize
and
identify
micrometer sized features at a
rate of about a Megahertz (H.
Kido and J.Zoval).
A CD as a Fluidic Platform
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The voltages from the photodetector are sent to
a computer using a fast A/D converter.
The image is then reconstitued using simple
graphics software
V
O
L
T
A
G
E
(H. Kido and J.Zoval).
TIME
A CD as a Fluidic Platform
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Examples of pictures taken
using the CD player.
Vision
is
another
dimension CD fluidics can
offer.
DNA array
Gnat wing
White blood cells
A CD as a Fluidic Platform
 The optical disc drive is a smart
centrifuge.
Center
R1
r
R2

Pc   (R2  R1)
2

Ps 
R2  R1
2
  R R
2
 cos  C
A
1
1
 cos C
 cos
2
fb  ( 2
) ( 2
)2
   R  R  4A
   R  R d H
A CD as a Fluidic Platform
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The
Compact
Disc
(CD)
is
a
biocompatible “solid phase” (plastic)
It
can
substitute
for
standard
consumables such as: slides, micro-wells,
centrifuge tubes.
A CD as a Fluidic Platform
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List of Lab tasks feasible on a
CD
– Mixing,
– Two-point calibration,
– Washing,
– Centrifuge,
– Sample splitting,
– Sample metering,
– Molecule separation,
– PCR,
– Fast Immuno-assays,
– Fast DNA- assays,
– Cell viability tests
A CD as a Fluidic Platform
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Cell lysis on the CD instead of using a vortex ---to
make further integration possible
Motivation: To extract DNA from cells in a CD
platform
The design below has a single lysis chamber
only.
A CD as a Fluidic Platform
Type: Chinese Hamster Ovary
(CHO-K1)
Size: ~10 µm
Glass Beads: 100 – 220 µm
No. of Rotation Cycles: 300 (5
min.)
E. coli Lysis
E.coli Lysis
DNA (ug/mL)
35
30
25
20
15
4:1 (15rps)
3:1 (15rps)
2:1 (15rps)
2:1 (20rps)
Vortex only
Volume Ratio of Solution to Beads
DNA concentration measured using PicoGreen Quantitation Kit
A CD as a Fluidic Platform
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Multiplex design allows the integration
of several cell lysis chambers with
other analysis tasks on the same
platform.
As we saw before the cells can also
be visualized before and after lysis
using the CD optics.
A CD as a Fluidic Platform
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Fast DNA Hybridization Detection
– Problem: Time consuming hybridization
caused by slow diffusion of DNA molecules
in passive DNA array approaches
– How to speed up hybridization ?
» Electrophoretic
» Mixing
» Flow
Microspots with
DNA Capture Probes
Out
Target
DNA
Injection
Flow-through Hybridization column
A CD as a Fluidic Platform
Modeling of DNA transport in flowthrough hybridization column
Total normal flux at the imobilized DNA probes
0.12
H=10um
H=15um
H=25um
0.1
Total normal flux
H=35um
0.08
0.06
0.04
0.02
0
Probe 1
Probe 2
Probe 3
Probe 4
Probe 5
Probe 6
Probe number
Navier Stokes eq.:
Species transport equation:
Probe 7
Probe 8
Probe 9
Probe 10
A CD as a Fluidic Platform
Hybridization in a constrained column using CD
platform for sample and reagent propulsion
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The flow cell consists of a hybridization column 1,
hydration buffer chamber 2, sample chamber 3, and two
rinse chambers 4&5.
 Fast hybridization steps:
Hydration
Sample flow
Two consecutive wash steps
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A CD as a Fluidic Platform
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The figure (a) on the left shows
the results of hybridization on
the CD.
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The figure compares a nonspecific sequence ssDNA (i)
with specific sequence ssDNA
(ii) hybridization experiment.
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A spinning velocity of 450 RPM
was used (corresponding to the
flow rate ranging from 0.65
uL/min to 1.3uL/min).
(i)
(ii)
(a)
(b)
A CD as a Fluidic Platform
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Final goal:
– Sample to answer nucleic acid analysis test
– Multi unit CD combining:
» Live/dead viability assay for cell quantization.
» Hybrization detection in which Cells are lysed, nucleic acids are purified
and mixed with RNAase inhibitor, calibrants, and reporters. Fast
hybridization using flow-through column
Live/dead viability unit
Fast Hybridization detection unit
A CD as a Fluidic Platform
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Diagnostics as a powerful new application of a very mature and well
established technology: CD, DVD, etc.
Sample to answer for molecular diagnostics in a hand-held is not about
if but when --microfluidics will make it possible and the CD approach
has the most features that fit the application’s need.
Don’t throw away your reject CD’s (AOL, Barry Manilow, the Bee Gees,
etc....).They may have some use after all. Put blood on the tracks !
DNA
RNA
bacteria,
cancer cell,
WBC, et al
Raw sample
Cell
Separation
Hybridization
Electrophoresis
Sequencing
protein
Cell Lysis,
Purification
Sample Preparation
Amplification
Nanofluidics
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As lithography tools go beyond
1 µm new fluidic possibilities
arise.
With fluidic channels of the size
of biological polymers we can
start interacting with these
species.
Figure on the right (H.
Craighead) demonstrates DNA
separation using nanochannels
(artificial hydrogel).
Microfluidic Challenges
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Wet reagent storage and dry reagent reconstitution
Tight liquid and vapor valves
Integrated microvalves and micropumps
Packaging
– Interconnects (optimize, reduce, eliminate)
– Filling / bubbles / dead volume
– Leakage
Surface functionalization
Microflow measurement and characterization
Control algorithms, data processing, and communications
Integrated, ultrasensitive detection
Heterogenous material integration
Sensitivity limited by sample volume (front end
amplifiers/concentrators?)
Low power
– Harness energy from host or ambient
– Low power pressure sources