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BIOMICROFLUIDICS. May 12, 2003 Final Report Susan Beatty Stacy Cabrera Saba Choudhary Dan Janiak. www.mae.ufl.edu. OVERVIEW. This illustration show the processing of a glass microfluidic device. http://www.mae.ufl.edu/~zhf/ResearchInterests-ZHFan.htm.
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BIOMICROFLUIDICS May 12, 2003 Final Report Susan Beatty Stacy Cabrera Saba Choudhary Dan Janiak www.mae.ufl.edu
OVERVIEW This illustration show the processing of a glass microfluidic device. http://www.mae.ufl.edu/~zhf/ResearchInterests-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 • 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 http://www.yourmedicalsource.com/images/pancreas.jpg
DRUG DELIVERY: NEURO-ACTIVE 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_400.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
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 • Begins with etching holes into silicon substrates from bottom http://touch.caltech.edu http://gmwgroup.harvard.edu
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.
