Transcript biomicrofluidics.fin..

BIOMICROFLUIDICS
May 12, 2003
Final Report
www.mae.ufl.edu
Susan Beatty Stacy Cabrera
Saba Choudhary Dan Janiak
OVERVIEW
This illustration show the processing
of a glass microfluidic device.
http://www.mae.ufl.edu/~zhf/Resear
chInterests-ZHFan.htm
• Microfluidics
Introduction
• Biomicrofluidics
– Lab-on-a-chip
– Drug delivery and
Micro-dosage systems
•Materials
–For Microfluidics
–For valves
•Processes
–For Microfluidics
–For valves
•Future of Microfluidics
MICROFLUIDICS
• The control of tiny amounts of gases or liquids in
a miniaturized system of channels, pumps, valves,
and sensors.
• The motivation stems from trying to be more
efficient on a smaller scale (several tests on a
single micro chip).
• Example in Nature: human body’s oxygen (blood)
transport system
• mTAS: systems of channels, valves, pumps,
detectors
MOTIVATION
• Macro scale = laminar,
random, and turbulent
flow
• Micro scale = laminar
flow
• Laminar flow allows
controlled mixing
• Low thermal mass
• Efficient mass transport
• Good (large) ratio of
channel surface area:
channel volume
http://www.spie.org/web/oer/august/aug00/microfluidics.html
BIOMEDICAL APPLICATIONS:
LAB-ON-A-CHIP
•Used for analyzing thousands of samples at
once
•Can perform clinical diagnoses, scan DNA,
run electrophoretic separations
•System: substrate with integrated
microchannels and devices
•Experiment: uses fluid sample in picoliter
range
•Advantage: conserve sample and time
LAB-ON-A-CHIP: GENE CHIP
•Also known as DNA chips or DNA
microarrays
•Used for analyzing thousands of Genes at once
•DNA probes and DNA sample
•Can analyze cancerous cells
•Can determine which genes or turned on or off
by a drug
•Advantage: accelerate the pace of genetic
research
GENE CHIP
http://www.popcouncil.org/images/gene_chip.gif
BIOMEDICAL APPLICATIONS: DRUG
DELIVERY AND MICRO-DOSING
SYSTEMS
•Needed in the medical field
•System: micropump and flowsensor
•High dosage approach used in the past
Insulin – wastage of insulin
Painkillers – possibility of addiction
http://www.yourmedicalsour
•Insulin micropump: mimic action of pancreas ce.com/images/pancreas.jpg
Microfluidics can make possible closed-loop system with
glucose sensor
•Painkillers: deliver drug locally, not globally
Avoid addiction
Tested at Maternity Hospital in Dublin, Ireland
DRUG DELIVERY: NEUROACTIVE COMPOUNDS
•Current research at Michigan
University on Neural Microfluidic
Devices for the intracerebral delivery
of neuro-active compounds
•Challenge: Must get the drug to CNS,
across blood-brain barrier and before
drugs are degraded and metabolized
•High dosage approach can have
detrimental effects on other parts of
body
•Challenge can be faced with
microfluidic technology
http://www.yourmedicalsource.com
/images/central_nervous_system_4
00.jpg
MICROFLUIDIC SYSTEMS:
PRODUCT OF DEVICE
INTEGRATION
•Many micro-devices: valves, pumps, fluidic mixers, and
sensors
•Device focus: Valves – needed to control flow of fluid
•Two types of Valves: Passive and Active
PASSIVE VS. ACTIVE VALVES
Passive Valves
No actuation required
Designed to give higher flow in one direction
Main application in mechanical micropumps
Flap is controlled by pressure difference across it
Active Valves: Slightly more complex
Need a form of actuation (thermal, electrical)
Actuation controls the flap
MATERIALS OVERVIEW
The type of material used depends on the structure or device
(mircochannel, pump, valve, etc…) being fabricated
-cost
-compatibility
MATERIAL
SILICON
PLASTICS
POSITIVES
Well understood
Highly available
Inexpensive
Disposable
Easily machined
NEGATIVES
Expensive
Not always bioinert
Swelling
Pairing
COMMON MATERIALS
PDMS – Polydimethylsiloxane
Used as a structural material for microchannels
Low interfacial free energy
Stable against humidity, temperature
Can be used as a stamp for processes such as
microcontact printing, micromolding
Parylene
Can be used as a structural material or coating
Low permeability to moisture
High resistance to corrosion
Polyimide
- Used for microchannels
- Easy to deposit metals (sputter)
MATERIALS FOR VALVES
Conjugated polymers
•“Organic semiconductors”
•Doping level depends on the oxidation state of the polymer
•Volume change associated with oxidation state
•Volume change occurs as a result of ions moving into and out of
the polymer
Large Immobile Anion:
Small Mobile Cation:
P+(A-) + C+ + e-  P(AC)
P+(A-) + C+ + e-  P + A- + C+
MATERIALS FOR VALVES
PEG (Polyethylene Glycol)
•Volume change associated with phase transition
Paraffin
•Volume change
Bimetallic Strips
•Expansion
http://www.wam.umd.edu/~smela
PROCESSES
• Overview
– Soft lithography
• Silicon is patterned with a negative photoresist
• Polymer is cast onto silicon mold
• Polymer is cured and removed from mold
http://nanotron.ecn.pudue.edu
PROCESSES CONT.
– micromachining
• Bulk micromachining
– Removes from bulk of material-etching
• Surface micromaching
– Adds to surface of material
» Deposistion
» Micro contact printing
VALVE PROCESSES
• Diaphragm check valve
http://touch.caltech.edu
http://gmwgroup.harvard.edu
• Begins with etching holes into silicon
substrates from bottom
VALVE PROCESSES CONT.
• Metal seals are deposited
• Photoresist and polymer are deposited
• Resist is removed with acetone and silicon
membrane is etched
http://touch.caltech.edu
FUTURE OF BIOMICROFLUIDICS
• Automation of complex experimental procedures
• Transformation of macroscale lab tests to a device
the size of a postage stamp, available to the
individual, with the skill of the technician
• More rapid DNA sequencing and general
biological procedures
• Key Factor: future fabrication techniques are
compatible with current batch processing
techniques
Small ridges along the channel walls can force mixing by a kneading motion,
http://depts.washington.edu/bioe/shrunklab.pdf.
QUESTIONS