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Microfluidics and BioMEMS
Introduction
13.1.2016
Sami Franssila & Ville Jokinen
Many keywords
• Microfluidics
• Bio-MicroElectroMechanical
Systems
• Lab-on-a-chip
• Can be used interchangably,
• Even though not exactly
synonyms
Multidisciplinary science
Microfluidics can mean many things:
1.
2.
3.
Fundamental science relating to micro and nanoscale fluids
(physics, chemistry)
Fabrication of microfluidic devices (engineering, materials science,
etc.)
Applications (a plethora of fields, engineering, chemistry, biology)
On this course we will focus on:
• Fundamental aspects of microfluidics and microfabrication
• Common features and advantages of microsystems
• Selected application fields (analytical chemistry,
biochemistry, cells/tissue on chip)
Start of an era: Gas
chromatograph on silicon
(1979):
-injector
-separation channel
-thermal conductivity
detector
Gas fluidics minor activity
compared to liquid fluidics
(which started in 1990)
Is microfluidics different ?
Some important features of microfluidics:
1. Laminar flow
2. Small size scales
3. Scaling effects
4. Parallelization and integration
Why miniaturize ?
• because it is possible?
• because it is improves
performance?
• because it opens up
new possibilities?
"Courtesy Sandia National Laboratories,
SUMMiTTM Technologies,
www.mems.sandia.gov"
1. Laminar flow
•
•
•
•
A key difference between micro and macrofluidics: laminar flow
Laminar flow means no turbulence. The streamlines are stable over time.
Laminar flow physics is easy (while turbulence is still somewhat unsolved)
Laminar flow is predictable, can be modeled and enables many
applications.
Turbulent vs. laminar flow
Turbulent = efficient mixing
Laminar: slow mixing by diffusion
Laminar flow application: odour sensing
Different odour-containing fluids are
directed past the nose of a worm
C.Elegans, which is kept stationary in
one channel.
Worm reactions to odours are
detected (by fluorescent calcium
receptor signal).
Buffer removes odour, and switching
to a different channel, a new odour is
brought to worm.
2. Small size scales
Microfabrication
Nanofabrication
• Many opportunities by fabricating structures at roughly the same scale as analytes.
Typical sizes in microfluidics
•
•
•
•
Microfluidic channels: width and height 10 – 100 µm, length 1 mm – 1 cm
Pores and gaps, > 10 nm
Volumes: a microfluidic chip 1 µl, ink jet droplets 1-10 pl
Size of a microfluidic chip, 5mm – 5 cm.
Micropumped systems
• Volume flow rates (Q) of micropumps are in the range of 1 nl/min to
1 ml/min (1 nl = 10-9 l = 10-12 m3)
• Volume flow rate Q = A *v [m3/s = m2*m/s]
• Linear flow rate v= Q/A
• Q = 1 nl/min = 10-12 m3/60 s = 16.7*10-15 m3/s
• If channel cross section is 100 µm*100 µm (10-4 m)
• v = 16.7*10-15 m3/s /(10-4*10-4 m2)=1.67*10-6m/s ≈ 2 µm/s
• Q= 1 µl/min  2 mm/s
3. Scaling effects
• Volume scales as d3
• Surface area scales as d2
→ Body forces to surface forces scale as d.
→ Micro and nanoscale is dominated by surface effects.
Example: A small glass capillary will fill spontaneously by capillary action
(surface force) even against gravity (body/volume force) while a garden hose
will not.
• Diffusion time scales as d2
→ Micro and nanoscale diffusion is fast and can even be used for mixing.
• Amount of analyte scales as d3
→ Amount of analyte can be low, detection methods need to be sensitive.
Scaling: diffusion & detection
Cube edge
1 mm
100 µm
10 µm
1 µm
Cube volume
1 µL
1 nL
1 pL
1 fL
100 s
1s
10 ms
6*108
6*105
600
Diffusion time (small protein) ≈ 3 hours
#molecules (1 µM)
6*1011
4. Parallelization and integration
• Microfluidic devices lend themselves well to parallelization due to the small size and
the parallel nature of many microfabrication processes.
• Lab-on-a-chip concept: everything necessary for the application is provided on chip.
(also called µTAS, micro total analysis system)
• Often in practice, lots of off chip equipment and connections used.
Large scale fluidic
integration
Protein interaction chip
256-mixer
S. Quake
Radiolabeling synthesis reactor for PET
Fluidic connectors
Ville Saarela, TKK
Chemical microfluidics
-separation systems (CE, LC, GC,...)
-detectors (microelectrodes, MS, photodiodes,...)
-droplet generators (ESI)
-ionization systems (corona, UV, ...)
-synthesis reactors
-gradient generators
-crystallization chips
-...
APCI-MS, Atmospheric Pressure Chemical
Ionization Mass Spectrometry
Drug delivery
100 identical drug
chambers
Drug release by
electrical
puncturing of a gold
membrane
Physical microfluidics
• cooling ICs and high power lasers
• power-MEMS: combustion engines, fuel
atomizers, fuel cells
• fluidic optical switching
• fluid sensors (rate, viscosity, shear, ...)
• MAVs = Micro Air Vehicles
• microrockets
• fluidic logic
Electronic paper by electrowetting
BioMEMS
• Microdevices for handling biomolecules, cells,
bacteria, viruses, tissue, model-organs
• All BioMEMS devices are microfluidic devices,
because biology takes place in water
Bio-MEMS Devices to Monitor Neural Electrical Circuitry
Andres Huertas, Michele Panico, Shuming Zhang
Sperm selection
Lung model (organ-on-a-chip)
Chip for mimicking lungs.
2 types of cells cultured
on opposite sides of a
stretchable membrane.
Stretching simulates
breathing-induced
mechanical movements.
Ingber et al. Wyss Institute
Microfluidic benefits
Many functions can be integrated in a single device
Small volumes lead to fast reactions
Sensitivity is enhanced because of
high surface-to-volume ratios
Laminar flow easy to control