biomicrofluidics may 12, 2003 final report susan beatty stacy cabrera saba choudhary dan janiak
TRANSCRIPT
BIOMICROFLUIDICSBIOMICROFLUIDICS
May 12, 2003
Final Report
Susan Beatty Stacy Cabrera
Saba Choudhary Dan Janiak
www.mae.ufl.edu
OVERVIEWOVERVIEW
• 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
This illustration show the processing of a glass microfluidic device.
http://www.mae.ufl.edu/~zhf/ResearchInterests-ZHFan.htm
MICROFLUIDICSMICROFLUIDICS
• 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
MOTIVATIONMOTIVATION
• 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
•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
BIOMEDICAL APPLICATIONS: BIOMEDICAL APPLICATIONS: LAB-ON-A-CHIPLAB-ON-A-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
LAB-ON-A-CHIP: GENE CHIPLAB-ON-A-CHIP: GENE CHIP
•Needed in the medical field•System: micropump and flowsensor•High dosage approach used in the past
Insulin – wastage of insulin
Painkillers – possibility of addiction •Insulin micropump: mimic action of pancreas
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
BIOMEDICAL APPLICATIONS: DRUG BIOMEDICAL APPLICATIONS: DRUG DELIVERY AND MICRO-DOSING DELIVERY AND MICRO-DOSING
SYSTEMSSYSTEMS
http://www.yourmedicalsource.com/images/pancreas.jpg
•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
DRUG DELIVERY: NEURO-DRUG DELIVERY: NEURO-ACTIVE COMPOUNDSACTIVE COMPOUNDS
http://www.yourmedicalsource.com/images/central_nervous_system_400.jpg
•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
MICROFLUIDIC SYSTEMS: MICROFLUIDIC SYSTEMS: PRODUCT OF DEVICE PRODUCT OF DEVICE
INTEGRATIONINTEGRATION
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
PASSIVE VS. ACTIVE VALVESPASSIVE VS. ACTIVE VALVES
MATERIALS OVERVIEWMATERIALS OVERVIEW
MATERIAL SILICON PLASTICS
POSITIVES Well understood
Highly available
Inexpensive
Disposable
Easily machined
NEGATIVES Expensive
Not always bioinert
Swelling
Pairing
The type of material used depends on the structure or device (mircochannel, pump, valve, etc…) being fabricated
-cost -compatibility
COMMON MATERIALSCOMMON MATERIALSPDMS – 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,
micromoldingParylene- Can be used as a structural material or coating- Low permeability to moisture- High resistance to corrosionPolyimide- Used for microchannels- Easy to deposit metals (sputter)
MATERIALS FOR VALVESMATERIALS 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 VALVESMATERIALS FOR VALVES
PEG (Polyethylene Glycol)
•Volume change associated with phase transition
Paraffin
•Volume change
Bimetallic Strips
•Expansion
http://www.wam.umd.edu/~smela
PROCESSESPROCESSES
• 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.PROCESSES CONT.
– micromachining• Bulk micromachining
– Removes from bulk of material-etching
• Surface micromaching– Adds to surface of material
» Deposistion
» Micro contact printing
VALVE PROCESSESVALVE PROCESSES
• Diaphragm check valve
• Begins with etching holes into silicon substrates from bottom
http://touch.caltech.edu http://gmwgroup.harvard.edu
VALVE PROCESSES CONT.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 BIOMICROFLUIDICSFUTURE 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.