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ECEN 414 Exam 1 questions and
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Biosensors - correct answer โโ Devices that combine a biologically sensitive element with a physical or chemical transducer to detect the presence of specific compounds in a given external environment Bio-recognition systems, typically enzymes or binding proteins on the surface of a physical or chemical transducer Transducer - correct answer โโ A system the converts one type of energy to another Bio-recognition Systems - correct answer โโ Enzymes Antibodies DNAs Bacteria Single cell organisms Tissues of higher organisms Biosensor Applications - correct answer โโ Medical research and diagnosis Point-of-care testing Food and environmental testing Bio-tech applications Micro-Electro-Mechanical-System (MEMS) - correct answer โโ Miniaturized devices and systems that have electrical and mechanical components
Manufactured using fabrication technologies from the semiconductor industry BioMEMS - correct answer โโ Lab-on-a-chip Has all the stages of chemical analysis Microfluidics - correct answer โโ Fluidic systems in which smaller size scale causes changes in fluid behavior Laminar Flow large surface to volume ratio Droplet Microfluidics - correct answer โโ Two-phase flow oil in water water in oil Why Miniaturization? - correct answer โโ Need to move analysis closer to the user EX: pregnancy test, blood glucose tests Advantages: Better performance due to smaller sample Low power consumption
Photolithography (Optical Lithography) - correct answer โโ Transfer of patterns from a mask to a substrate by exposing UV light through a mask on a substrate Mask - correct answer โโ Created by direct writing (E-beam) or lactic exposure on a photoresist coated glass Positive Photoresist - correct answer โโ Exposure to light destroys the polymer crosslink and becomes more soluble in developer Negative Photoresist - correct answer โโ Exposure to light forms crosslink and becomes less soluble in developer Lithography Process - correct answer โโ Spin-coat photoresist Soft-bake (90-95 C) Align/Exposure Develop Photomasks - correct answer โโ High precision plates containing microscopic images such as electronic circuits. They are made from very flat pieces of quartz or glass with a layer of chrome on one side. Etched in the chrome is a portion of an electronic circuit design. Geometry - correct answer โโ circuit design on the photomask Clear Field Mask - correct answer โโ Clear background area surrounding the component geometry geometry shows up dark
Typically used for a POSITIVE photoresist Dark Field Mask - correct answer โโ Dark background area surrounding the component geometry geometry shows up clear Typically used for a NEGATIVE photoresist Thin Film Deposition - correct answer โโ Thermal oxidation on silicon wafer Dry oxidation: High quality but slow deposition time Wet oxidation: Faster deposition time but lower quality High temperature (800-1100 C) Dry/Wet/Dry steps Important Metal Film Properties - correct answer โโ Low resistivity Easy to etch Good adhesion Low stress Surface smoothness
3D micro machining possible greater surface roughness than embossing or injection molding Stereolithography (SLA) - correct answer โโ 3D micro manufacturing process using photopolymerization Laser beam scans the surface of a photo-curable liquid polymers layer by layer to produce copies of solid or surface models Rapid prototyping and easy production of multiple copies Soft Lithography - correct answer โโ A micro fabrication technique where polymer microstructures are fabricated by replicating structures on a prefabricated micro mold Polydimethylsiloxane (PDMS) - correct answer โโ A liquid phase two part polymer composed of resin and curing agent Most commonly used soft lithography material Flexible, transparent and bio-compatible Simple and low cost Surface is typically hydrophobic but changes to hydrophilic when exposed to oxygen plasma
Spin Coating - correct answer โโ Typically used in photolithography process to coat the substrate with photoresist to a desired thickness Thickness of the coating material can be adjusted by controlling the spin rate Microfluidic Components - correct answer โโ Single Layer: Chambers, reactors and channels Multiple Layer: Valving, pumping, mixing, metering Cast Molding Advantages - correct answer โโ Low cost Good pattern replication capability Soft flexible material Opiticaly transparent Self adhesion to other PDMS Reversible sealing is possible Non-toxic Laminar Flow - correct answer โโ Low Renyolds number < 1 Provides a means by which molecules can be transported in a relatively predictable manner through micro channels Microvalve - correct answer โโ A pressure containing mechanical device used to shut off or otherwise modify the flow of a fluid that passes through it Passive Microvalve - correct answer โโ Simple structure
Should not be affected by its past history of measurements Bio-Compatibility Electrochemistry - correct answer โโ Study of phenomena caused by charge transfer process at the electrode/solution interface Advantages of Electrochemical Detection - correct answer โโ Specificity Selectivity High sensitivity Low detection limit Real-time or close to real-time analysis Miniaturization is easy Redox potential - correct answer โโ The voltage measured when a half-cell is connected to a standard hydrogen electrode Voltage where oxidation-reduction process occurs Enzyme - correct answer โโ Protein molecules which serve to accelerate the chemical reactions of living cells Catalyze reactions by lowering the activation energy Enzyme Classification - correct answer โโ All enzymes catalyze transfer reactions: electrons, atoms or functional groups Oxidoreductase: transfer electrons
Transferase: transfer functional groups Hydrolase: transfer functional group to water Lyase: Bond cleavage by means other than hydrolysis and oxidation Isomerase: transfer groups within molecules Ligase: bond-formation reactions Immobilization - correct answer โโ Fixing enzymes to carrier materials Enzymatic behavior alters Stabilized Immobilization Methods - correct answer โโ Physical: adsorption, entrapment Chemical: covalent attachment, cross-linking Combination of the two Adsorption - correct answer โโ Simplest method of immobilization Molecules not absorbed can be removed by washing Is a reversible process Bonding is weak, short time span Carrier: high affinity and capacity for biomolecules, should not absorb reaction products or inhibitors of the enzyme Enzyme: must remain active in the absorbed state Active charcoal, aluminum oxide, porous glass
Inhibition: enzyme binds inhibitor, competes with substrate Clark Oxygen Sensor - correct answer โโ First amperometric sensor developed in 1956 Electrochemical monitoring of oxygen depletion or hydrogen peroxide formation Glucose Sensing Options - correct answer โโ Following disappearance of oxygen Following appearance of hydrogen peroxide Following pH changes Affinity Interaction - correct answer โโ Multiple non-covalent interactions between two species leading to the formation of a molecular aggregate usually called a complex reversible process very specific Antibody - correct answer โโ A large protein produced in the bodying response to antigens such as viruses and bacteria Specific binding between antibodies and antigens Antigen - correct answer โโ Certain regions will bind to an antibody Binding region is called epitope
Detection of this antibody-antigen complex allows for identification of the target antigen Polyclonal - correct answer โโ Antibodies from a variety of immune cells that bind to an antigen Bind to different epitope of the antigen Monoclonal - correct answer โโ All produced by the same cell Generated by cloning Typically used in biosensors Immunosassay - correct answer โโ Analytical procedure based on antigen- antibody reactions that can be used to determine either member as the analytic Non-Labeled Detection - correct answer โโ Detect changes in physical properties Impedance based: Two electrodes on either side of enzymes, once enzymes are bonded, the electrode connection is stopped Cantilever based - correct answer โโ Mass detection: mass change causes resonance frequency of the cantilever to change Stress change detection: motion originates from the free-energy change induced by specific bimolecular binding that can be optically detected
