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125 Cards in this Set
- Front
- Back
In order of how fast they adsorb to a material surface, rank: cells, proteins, and monolayer of proteins. |
Proteins followed by a monolayer followed by cells |
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Receptors on cell bind to what for what purpose? |
Receptors on cells bind to ligand proteins on the surface of biomaterials which affect cell proliferation, differentiation, migration, and death. |
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Do hydrophilic materials resist or favor protein adsorption? Why? |
Hydrophilic RESISTS proteins because strongly bound water molecules repel protein |
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Do hydrophobic materials resist or favor protein adsorption? |
Hydrophobic FAVORS proteins |
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What are 5 applications of surface modification? |
1. Improve tissue compatibility 2. Blood compatibility 3. Antibacterial properties 4. Corrosion resistance 5. Wear resistance |
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What is Surface Modification? |
A process that alters one or more surface properties while retaining the bulk properties of a material. |
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What 3 surface properties are altered? |
1. Surface composition 2. Topography 3. Surface charges |
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Surface modifications should be what 3 things to promote commercialization? |
1. Simple 2. Robust 3. Cost-effective |
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What are two types of subtractive surface modifications? |
1. Abrasive Blasting 2. Plasma Glow Discharge Treatment |
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Abrasive blasting techniques are commonly used for what? |
Preparing material surfaces for further treatment, cleaning, or finishing of a surface, and shot peening. |
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What is Shot Peening? |
A process used to increase strength and durability by replacing tensile surface stresses with compressive stresses. |
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In medical devices, abrasive blasting is done to do what 5 things? |
1. Remove surface contaminants, 2. Roughen implant surfaces, 3. Increase the surface area, 4. Enhance cellular-biomaterial interaction 5. Improve the adhesion of coatings. |
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What are the 3 basic components of an abrasive blast system? |
1. Blast media 2. Accessories in the blasting equipment 3. Air compressor |
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What is the mechanism behind abrasive blasting? |
Use of air compressor to propel a stream of blasting media against a surface under pressure |
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What are 6 parameters in which abrasive blasting is dependent? |
1. Type of abrasive media used 2. Size and shape of abrasive media 3. Substrate type 4. Gas or air pressure 5. Type of nozzle used 6. Nozzle to substrate distance |
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What are 4 types of abrasive media used? |
1. Glass beads 2. Sodium bicarbonate 3. Alumina (cuz its hard) 4. Calcium phosphates (resorbable blast media)
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What is the general size and shape of abrasive media? |
10 to 50 um with round or irregular shapes |
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Why are resorbable blast medias used? |
RBM like calcium phosphate are used because they're biocompatible and may have osteoconductive properties. |
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What are 2 applications of abrasive blasting? |
1. Surface preparation: roughen to improve adhesion 2. Surface finish: roughen for resorbable blast media like dental implants |
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What is a problem with abrasive blasting? |
The embedment of abrasive media in the substrates which can lead to stress concentration points. |
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What are the 2 types of Plasma glow discharge treatments? |
1. Local thermal equilibrium (LTE) 2. Non-local thermal equilibrium (non-LTE) |
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What are the 3 basic components of plasma glow discharge treatments? |
1. Chamber 2. Electrodes 3. Reactive or inert gas |
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What is the mechanism by which plasma glow discharge treatments work? |
Gas molecules in the chamber are ionized due to a potential difference being applied between to electrodes. Positively charged ions bombard the cathode thereby releasing secondary electrons. |
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In a simple glow discharge, what is the cathode? |
The material to be modified |
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In plasma glow discharge treatments, what is responsible for the characteristic glow? |
Excitation or elevation of energy levels of the gas molecules being ionized followed by their decay |
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What is Local thermal equilibrium plasma glow discharge treatment? |
All plasma species in localized area exhibit similar temperatures. |
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What are 5 applications of LTE plasma glow discharge treatments? |
1. Cutting 2. Welding 3. Spraying 4. Analytical analysis such as Inductively Coupled Plasma (ICP) 5. Any applications that require high uniform temperature |
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What is a application of non-LTE plasma glow discharge treatments? |
Deposition of layers or etching where high temperatures are not required |
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A simple glow discharge chamber or cell can be made by doing what? |
Inserting a cathode and an anode into the cell or by having the walls of the cell act as these electrodes. |
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In plasma glow discharge treatment, ionization results in what? |
The physical removal of electrons from an atom or molecule in the gaseous state at low pressure where they are accelerated toward the anode. |
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Ionization in plasma glow discharge treatment results in what? |
Production of positive ions and electrons |
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When the outside excitation source is a direct current, what is created? |
Plasma is created when a potential difference of a few hundred volts to a few kilovolts is applied between the two electrodes. |
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What are 2 problems with DC glow discharge? |
1. The inability to use a non-conducting electrode in the chamber or cell. 2. Buildup of electrons due to constant current leads to burn-out of the glow discharge |
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What are the 2 types of radiofrequency glow discharge? |
1. Capacitively coupled RF glow discharge 2. Inductively coupled RF glow discharge |
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In the capacitively coupled RF glow discharge, the cathode is typically connected to what? The electrodes and their sheaths form what? |
A RF power supply and the electrodes and their sheaths form a capacitor. |
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What is the inductively coupled RF glow discharge? |
A electrodeless discharge in which the chamber is surrounded by a coil thus allowing the RF power to be inductively coupled to the plasma. |
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What is one of the common commercially accepted methods for depositing hydroxyapatite and titanium? |
Thermal spraying |
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What is Thermal Spraying? |
A line-of-sight process that uses a gas stream to carry powders, which are then passed through a plasma. |
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What gases are usually used as primary gases in thermal spraying? |
Argon and nitrogen |
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What gases are usually used as secondary gases in thermal spraying? |
Hydrogen and Helium |
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What 2 things influence coating crystallinity in thermal spraying? |
1. Type of gas used 2. Gas ratios |
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Compared to Nitrogen, does Argon produce a thicker or thinner coating? |
Thinner coating |
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Thermal spraying requires the presence of what 3 things? |
1. Electric heat source in plasma spraying; chemical heat source in flame spraying 2. Media supply 3. A feeder or mechanism to introduce the powder particles to the heat source |
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In thermal spraying, how is the substrate surface prepared? |
It is prepared by plasma spraying to enhance coating-substrate adhesion. |
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Coatings with a lower percent porosity and impurities can be obtained using which plasma spraying technique? |
Vacuum spraying (instead of air plasma spraying) |
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What are the 3 types of thermal spraying? |
1. Plasma spraying (highest temp) 2. Flame spraying (highest deposition rate) 3. High-velocity oxyfuel (fastest velocity) |
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In thermal spraying, the higher the temperature means what? |
Higher the decomposition |
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In thermal spraying, a higher deposition rate means what? |
Thicker coatings |
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In thermal spraying, lower particle velocity means what 2 things? |
1. Lower bond strength 2. Higher porosity |
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Properties of the coatings in thermal spraying depend on what 7 things? |
1. Distance between nozzle and substrates 2. Powder size 3. Speed and temperature of the plasma 4. Rate of cooling 5. Gas used and flow rate 6. Energy output 7. Spray time |
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In thermal spraying, the sprayed droplets become what? |
Flattened lamallae upon depositing on the substrate surface whose thickness and lateral dimensions depend on the size of the powders. |
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Which has a higher coefficient of thermal expansion: metals or ceramics? Why is this important? |
Metals. Differences in metal and ceramic coatings can lead to cracks |
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Why are secondary gases used in thermal spraying? |
To alter the plasma characteristics and energy level |
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In the case of metallic substrates, a higher coating temperature may do what? |
Increase the substrate temperature leading to oxidation that can be detrimental to the coating-substrate bond. |
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Rapid cooling of thermal sprayed coatings results in the formation of what kind of coating? |
Amorphous |
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Rapid solidification of coatings during thermal spraying results in the formation of what? |
Cracks in the coating |
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What is the major difference between plasma spraying and flame spraying? |
Flame spraying uses an oxy-acetylene burner as the heat source. |
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Although the deposition rate of the high velocity oxy fuel spraying process is similar to that of plasma spraying, the coatings produced are what? |
Denser with high coating-substrate bond strength than coatings done by flame or plasma spraying.
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What is Physical Vapor Deposition? |
Term that refers to a family of line-of-sight vaporization coating techniques for depositing thin films on substrates. |
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What are the 4 basic steps of Physical Vapor Deposition? |
1. Evaporation of target material 2. Transportation of the dislodged atoms to the substrate 3. Possible reaction of dislodged atoms with reactive gas 4. Deposition of the atoms on the substrate surface |
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The physical vapor deposition process involves the transfer of what where? |
The transfer of material on an atomic level in a vacuum chamber |
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What are the 4 types of Physical Vapor Deposition? |
1. Evaporative 2. Pulsed Laser 3. Ion Implantation 4. Sputter deposition |
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What are the 2 basic mechanisms involved in Evaporative Deposition? |
1. Target material is melted using an electric heater 2. Rise in vapor pressure allows vapor to be deposited on the substrate |
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In Pulsed Laser Deposition, the penetration of the laser pulse into the target surface results in what? |
Results in electronic excitation of the target due to the removal of electrons from its atoms which then go on to collide with target atoms and gas atoms in the chamber. |
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In Pulsed Laser Deposition, the collision of electrons leads to what? |
A plasma plume being formed which then bombards the substrate surface with target materials. |
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In sputter deposition, what are the 2 basic mechanisms? |
1. Erosion of target material by high energy gaseous ions 2. Energy of the ejected atoms is transported to the substrate |
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What are 4 types of sputter deposition? |
1. DC sputtering 2. Radiofrequency sputtering 3. RF magnetron sputtering 4. Ion beam sputtering |
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What mode of sputter deposition is used for conductive materials? |
DC sputtering |
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DC sputter deposition requires what? |
A continuous potential difference between the cathode and anode |
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The use of non-conductive materials in DC sputter deposition leads to what? |
A short breakdown, followed by the creation of a surface charge on the cathode |
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What mode of sputter deposition is used for non-conductive target materials? |
Radiofrequency sputter deposition |
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Which has the lower sputtering rate: radiofrequency or DC sputter deposition? |
Radiofrequency sputter deposition |
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The combined use of magnetron with sputtering allows what? |
More effecient sputtering rate, minimal growth of insulating films, and independent control of bombardment of the growing film |
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What are the 2 examples of modified Ion beam sputter deposition processes? |
1. Ion beam-assisted deposition (IBAD) 2. Dual ion beam sputter deposition |
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Unlike the other sputtering modes, the target used in ion beam sputtering is not used as what? Why is this important? |
A cathode and thus the electrical conductivity of the target is no longer of important |
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What is the principle behind ion beam-assisted deposition? |
The interaction of the accelerated ions generated by the ion source with the coating atoms from the PVD process as they are being deposited on the substrate surface. |
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Compared to other sputtering processes, IBAD coatings are what 2 things? |
1. Thinner 2. Denser |
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What is ion implantation? |
A process whereby high-energy accelerated ions penetrate or embed into the substrate material. |
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Ion implantation results in what? |
Penetration of ions into the substrate, causing structural damages to the surface. |
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Ion implantation does what to the mechanical properties of substrates? |
Alters mechanical properties through formation of new phases at the near-surface region |
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What is Chemical Vapor Deposition? |
A chemical process using thermal energy to heat up gases in the coating chamber and drive the deposition reaction. |
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Chemical vapor deposition is used for depositing what? |
Metal and ceramic coatings |
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What are the 5 basic processes of Chemical Vapor deposition? |
1. Introduction of gas reactants in chamber 2. Moving gas reactants towards the heated substrate 3. Absorbing gas reactants on the heated substrate surface 4. Chemical reaction at the substrate forms coating 5. Desorption and evacuation of gas by-products from chamber |
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For Chemical Vapor deposition, what are the 2 requirements of the gas reactants? |
1. Volatile at high temps 2. Stable for delivery to heated surface |
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What are the 2 types of Chemical vapor deposition reactions? |
1. Homogenous 2. Heterogenous |
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When do homogenous reactions occur between gas reactants? |
As they move toward the heated substrates which results in the formation of gas-phase aggregates. |
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When do heterogenous reactions occur? |
When the gas reactants first adsorb on the heated substrate surfaces |
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Which form porous or low density coatings: homogenous or heterogenous reactions? |
Homogenous reactions! |
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Which is the more desired reaction due to forming denser coatings: homogenous or heterogeneous reactions? |
Heterogeneous reactions! |
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What is the problem with Chemical Vapor deposition? |
Many of the reactants or gases used are toxic, corrosive, explosive, and flammable. |
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What is grafting? |
Surface modification technique used to alter surface properties for selective protein adsorption. |
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Grafting requires what? |
The reaction of 1+ polymeric species or functional groups to the main chain of the polymeric macromolecules. |
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In grafting, attachment of functional groups is done through what 4 methods? |
1. Covalent coupling 2. Surface graft polymerization 3. Surface segregation 4. Interpenetration |
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Grafting process requires either of what 2 things? |
1. Chemical activation 2. Radiation |
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What 4 factors affect the properties of a grafted polymer layer? |
1. MW of polymer 2. Degree of chain branching 3. Density of functional and charged groups 4. Solubility of polymer |
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As listed in class, which functional groups are reactive? |
OH, COOH, NH2 |
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What are the 2 requirements of chemical grafting? |
1. Substrate surface contains active H 2. Solution contains functional species |
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Graft initiators or catalysts act on the substrate to do what? Why? |
Remove active hydrogen to create active sites or free radicals |
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What is a problem with chemical grafting? |
The need to remove oxygen from the aqueous solution |
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What type of grafting does not depend on graft initiators or catalysts? |
Radiation grafting |
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In radiation grafting, what 5 energy sources create the active sites on the substrate? |
1. Gamma radiation 2. UV 3. Corona discharge 4. Radiofrequency glow discharge 5. Electron beam radiation |
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What are the 3 basic steps to radiation grafting? |
1. Pre-radiation of substrate while in solution to create active sites by breaking bonds 2. Monomers covalently bond to substrate at the active site 3. Propagation of monomer through C-C bonds |
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The rate and efficiency of initiation in radiation grafting is dependent on what 4 things? |
1. Type of radiation 2. Dose or total energy absorbed 3. Dose rate 4. Radiation sensitivity of substrate |
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What is the Self-assembled monolayer technique? |
SAM deposits a monolayer thin film of organic molecules on surfaces to improve surface properties for corrosion rates, reducing friction, or enhancing wetting or adhesion. |
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What is the basic process of SAM? |
Samples are immersed in a solution containing SAM molecules |
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What are SAM molecules? |
Amphiphilic molecules containing both hydrophobic and hydrophilic properties |
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Which end of SAM molecules binds to the substrate? |
Hydrophilic heads |
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Which end of SAM molecules is away from the substrate? |
Hydrophobic tail ends |
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What part of SAM molecules can be functionalized? |
Hydrophobic tail ends |
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What are the 2 critical conditions that must occur for SAM formation to take place? |
1. Chemisorption of the head group to the substrate surface 2. 2D organization of SAM molecules through inter-chain interactions of hydrocarbon backbone |
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Van der Waal forces between carbon chains in SAM molecules allow them to do what? |
To form densely packed, semi-crystalline or crystalline monolayers |
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Monolayer formation in SAM is governed by what 4 things? |
1. Time of annealing 2. Cleanliness of substrate surface 3. Purity of solution 4. Properties of head and tail groups |
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The shorter the hydrocarbon backbone in SAM leads to what? |
More packed monolayer |
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The longer the hydrocarbon backbone in SAM leads to what? |
More interactions |
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SAM can be rapid but is dependent on what 2 things? |
1. Initial solution concentration 2. Temp |
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Which solution takes a longer time to reach a well-ordered state when assembled: concentrated solutions or dilute solutions? |
Concentrated solutions |
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What are 2 advantages of SAM? |
1. Simple and rapid 2. Can be used for planar and non-planar substrates |
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What are 2 types of patterning techniques of SAM? |
1. Micro-contact printing (planar or rolling stamp) 2. Dip-pen nanolithography |
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Layer-by-Layer film assembly is what kind of surface modification technique? |
Bottom-up |
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What is the process of layer-by-layer assembly? |
Films are formed by alternatively dipping the substrate into soluble anionic and cationic polyelectrolytes |
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What 2 things can be incorporated during alternate dipping in LbL? |
Proteins and growth factors |
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What 4 things affect LbL? |
1. Chemical structure and MW of polyelectrolytes 2. Ionic strength of polyelectrolytes 3. pH of electrolyte 4. Time in between dipping |
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What are the 2 types of LbL? |
1. Spin-coating 2. Spray |
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What are 2 disadvantages of spin-coating LbL? |
1. Restriction in the substrate size 2. Inability to effectively deposit monolayers on non-planar substrates |
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What 3 things influence the monolayer deposition using spray-LbL? |
1. Spraying time 2. Polyelectrolyte solution 3. Distance and angle of spray |