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BIM 109 > Midterm 2 > Flashcards

Midterm 2 Flashcards

1
Q

What are orthopedic materials ?

A
  • Fracture fixation device (Stop movment)
  • Spinal fixation device
  • Fracture plates
  • Wires pins screws artificial ligament
  • Joint replacement (replace function movement)
  • Hip keen ankle shoulder elbow wrist finger arthroplasty
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2
Q

What are two orthopedic types?

A
  • Osteoconductive (bone grows on implant surface)
  • Def: The property of a material that enables integration of new bone with the host bone
  • Osteoinductive (recuit cells & promotes osteogenisis)
  • Def: Characteristic of materials that promote new bone growth
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3
Q

What are two common joint replacements that are successful?

A

Hip and Knee

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4
Q

How long do total joint replacements last?

A

10-15 years it has a lifetime suitable for people only needed it for two decades (elderly).

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5
Q

Why might sex/gender be variable?

A
  • Lifespan
  • Bone degradation → Osteoporosis
  • Pregnancy
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6
Q

Why women easy to get? (59% are female)

A
  • Less Ca2+
  • Decrease in estogen
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7
Q

What are 3 joint preserving operations?

A
  • Arthroscopy 关节镜检查
  • Cartilage transplantation 软骨移植(Cartilage does not regenerate well → few cells)
  • Osteotomy (Sculpt bone) 截骨手术
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8
Q

What are 3 options for arthroplasty (surgery to restore jonint)?

A
  • Hemiarthroplasty
  • Resurfacing arthroplasty
  • Total joint arthroplasty
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9
Q

List 5 properties of orthopedic materials.

A
  • No toxicity or byproducts
  • Suitable mechanical strength
  • High wear resistance
  • Minimize stress-shielding
  • Osseo-integration abilities
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10
Q

What is metals exist as?

A

Oxides → Fe2O3 (rust), Al2O7, TiO2

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11
Q

What are mechanisms of corrosion 失升阴氧 得降还阳

A

Redox → Oxidation(generate electrons) – Reduction(consume electrons)

Oxidation loss e reduction gain e.

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12
Q

How are toxic metals processed in your body?

A
  • Metal atom becomes ionized and go into solution.
  • Metal atom combines with oxygen (or other species in solution) to form a compound that flakes off or dissolves (loss of mechniecal categrity)
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13
Q

What is the mechanism of corrosion in an acidic environment?

A
  • Metal → Metal2+ + 2e-(anode: oxidation) [e generate]
  • 2H+ + 2e- → H2 (cathode: reduction) [e consumed]
  • Total: Me+ + 2H+ → Me2+ + H2
  • Examples are Zn, Fe
  • The metal is oxidized (electrons taken) from anode electrons reduce hydrogen to form hydrogen gas cathode
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14
Q

What is the mechanism of corrosion in a neutral environment?

A
  • Metal → Metal2++2e- (anode: oxidation) [e generate]
  • 1/2 O2+H2O+2e- → 2OH- (cathode: reduction) [e consumed]
  • Me + 1/2 O2 → Me(OH)2
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15
Q

How does iron rust in water?

A
  • iron is oxidized
  • reduction in oxygen-containing aqueous solution
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16
Q

Choose: A high chance to consume electronics means a (low/high) electrode potential (E0)?

A

high

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17
Q

Choose: A more inert electrode means a (low/high) electrode potential (E0)?

A

high

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18
Q

What is the electrode half-reaction associated with an electrode potential (E0) of 0.00

A

2H+ + 2e- → H2

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19
Q

What are the requirements for galvanic corrosion?

A
  1. There must be 2 different metals.
  2. They must be electrically connected by an electrolyte（biological fluid）.
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20
Q

Choose:

In galvanic corrosion the less noble metal becomes the (anode/cathode) and corrodes (slower/faster) than by itself.

A

Anode; faster

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21
Q

What are 3 ways to prevent corrosion?

A
  1. Avoid using multiple metals
  2. use metals of similar nobility
  3. Passivation method (coating)
    Organic (e.g. paint polymers)
    Oxidation (e.g. Ti)
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22
Q

Corrosion is what type of reaction?

A

Oxidation reduction (redox). (Oxidation generated at the anode reduction consumed at the cathode )

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23
Q

what is cyclic loading?

A

Def: Loading an implant again and again and again (eg. joints are loaded 107 in 20 years).

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24
Q

Is static or cyclic loading better for testing your medical device?

A

Cyclic

It causes more damage (cracks defects) and increase risk of faliure.

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25
Q

Describe the steps of aseptic loosening.

A

1) particles generated around implant.(increase over time)
2) immune system responds
3) surrounding environment becomes acidic
4) metals corrosion bone degradation can cause movement of implant

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26
Q

Stress-shielding creates osteopenia (decrease bone density)

do you know it?

A

do you know it?

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27
Q

What is wolff’s law?

A

Def: As bone experiences stress the bone density increases

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28
Q

Why would using a degradable polymer implant help prevent negative consequences of stress shielding?

A

As the bone heals the polymer degrades. Once the polymer is fully gone your body can no longer rely on the polymer for help and will increase bone density according to Wolff’s law.

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29
Q

Metallic implants → match material properties

do you know it?

A

do you know it?

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30
Q

define Osseo-integration

A

Def: the formation of a direct interface between implant and bone without intervening soft tissue.

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31
Q

what are important aspects of Material design for osseointegration?

A
  • Interfacial design between the artificial joint and the surrounding bone.
  • Material design geometry of the articulating surface.
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32
Q

What are two types of osse-intergration?

A
  1. Glue
    Polymethylmethacrylate (PMMA) cement adheres metal to bone. (strong & dont have time for elderly people; definitive lifespan)
    A porous coating on the metal surface to create a bone ingrowth interface. (initially not as strong & strong eventually )
  2. Texture
    Add texture on the scales
    Can be used with cement
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33
Q

advantages/disadvantages of stainless steel (temporary implants)

A

Advantages
low cost
easy working
good mechanical properties in cold-worked conditions
Disadvantages
Least corrosion-resistant especially in high stress areas
Presence of nickel — allergies

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34
Q

advantages/disadvantages of cobalt alloys (metal/metal implants requiring strength)

A

Advantages
corrosion resistance in chloride environments(no pitting corrosion)
Casting alloy
High strength
Disadvantages
possible release of chromium
high cost
nickel and chromium allergies

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35
Q

advantages/disadvantages of titanium alloys (long term implants surgical tools and external prosthetics)

A

Advantages
low density
good mechano-chemical properties
best biocompatibility
Disadvantages
high cost
Sensutuivily to fretting
Low stress-shielding

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36
Q

what are components of hip implants?

A
  • Acetabular cup
  • Polyethylene insert (can also be ceramic [UHMWPE])
  • Metal femoral head
  • cobalt-chromium alloy or ceramic
  • Femoral stem
  • titanium and cobalt-chromium
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37
Q

What metal is suitable for a long term implant with low toxicity?

A

Titanium and titanium alloys for osseointegration

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38
Q

photo, bone healing cascade, page 5

do you know it?

A

do you know it?

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39
Q

What are the 3 main sections of long bones?

A
  1. Periosteum
  2. cortical bone
  3. marrow
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40
Q

What is the difference between an osteoblast and an osteroclast?

A
  • Osteoblasts create new bone * Osteoclasts eat bone
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41
Q

In the bone healing process what tissues form before the bone becomes normal??

A

1) hematoma
2) soft callus/unmineralized cartilage
3) fibrous tissue
4) hard callus/secondary bone
5) hard callus/remodeled bone
6) normal bone

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42
Q

After a bone is broken describe what happens after a) 1 day b) 1 week c) 1 month and d) multiple years

A

a) hematoma formation immune cells are recruited
b) soft callus formation stem cells recruited osteoblasts and chrondrocygtes recruited
c) hard callus and remodeled bone is formed deposit matrix is formed osteocytes live in the bone
d) normal bone replaces remodeled bone and it goes back to how it originally looked

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43
Q

What are some common uses of metals as biomaterials?

A
  • Bone and joint replacement
  • Dental implants
  • Tantalum foam allows for good tension and compression
  • Porous texture causes better osseointegration and cell migration
  • Maxillofacial and craniofacial reconstruction (颌面重建、颅面重建)
  • Cardiovascular devices
  • pacemaker case 起搏器
  • Defibrillator 除颤仪
  • Stents
  • External prostheses
  • Surgical instruments
  • Catheters
  • Medical tubing
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44
Q

What types of medical devices are metals most suitable for?

A
  • Load bearing implants
  • Internal fixation devices
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45
Q

What are key properties of metals?

A
  • Strong
  • Don’t bend much
  • Don’t degrade
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46
Q

What happens to material properties when you process metals?

A
  • High tensile strength
  • High fatigue strength
  • High yield strength
  • Low reactivity
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47
Q

For a processed metal what are 2 ways to control the material properties?

A
  1. Change the processing method
  2. Change the purity of the metal
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48
Q

List 6 physical properties of metals

A
  1. Luster (shininess)
  2. Good conductor of heat and electricity
  3. High density
  4. High melting point
  5. Ductile — most metals can be drawn out into thin wires
  6. Malleable — most metals can be hammered into thin sheets
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49
Q

What is the purpose of an Ashby plot?

A

To compare two physical material properties.

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50
Q

What is the x and y axes on an Ashby plot?

A

Any physical properties on x and y axes (e.g. luster heat conductivity electrical conductivity density melting point ductility malleability).

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51
Q

photo, ashby plot, page 7

A

Notice how metals/alloys and ceramics are in the top right because they are dense and strong. Wood is strong but less dense so it is at the left middle.

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52
Q

What are common chemical properties of metals?

A
  • Easily lose electrons (conductivity corrosion [redox reaction])
  • Surface reactive (easily forms oxides and hydrates)
  • Oxide: reaction with O2
  • Hydrates: coordinated with water
  • Loss of mass (some corrode easily)
  • Change in mechanical properties
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53
Q

What is an example of changing mechanical properties

A

Rusting (corrosion) forms Fe2O3 the rust flakes off. This weakens the metal and may be toxic for an implant.

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54
Q

Why do metals have a high melting and boiling point?

A

Metals have many strong metallic bonds so a lot of heat is required to break the bonds.

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55
Q

Why are metals good conductors of electricity and heat?

A

Metals have lots of free electrons that can move and carry charge.

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56
Q

Why are metals malleable and ductile?

A

Layers of positive ions can easily slide over another layer. The metallic bonds aren’t broken so the metal is still strong. This is why hammering metal will not break metallic bonds.

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57
Q

photo, periodic table, page 8

do you know it?

A

do you know it?

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58
Q

Define a unit cell of a crystal structure

A

The smallest repeating unit within a crystal lattice that retains all the structural and symmetry features of the crystal.

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59
Q

How are unit cells described?

A

Lengths (a b c) and angles (α β γ)

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60
Q

Give the lengths and angles of a cubic unit cell

A
  • a=b=c
  • α=β=γ=90°
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61
Q

For a cubic unit cell: Where are the atoms positioned? How many atoms fit into a single unit cell? What are the properties? Give an example material.

A
  • Atoms positioned at each vertex
  • 1 atom per unit cell
  • Low density rate
  • Polonium
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62
Q

For a body centered cubic (BCC) unit cell: Where are the atoms positioned? What are the properties? Give an example material.

A
  • Atoms positioned in each corner one extra atom in the center
  • 2 atoms per unit cell
  • Higher density than cubic ductile plastic (easy to work/deform)
  • Chromium tungsten tantalum molybdenum -iron (different phases of some materials have different unit cells)
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63
Q

For a face centered cubic (FCC) unit cell: Where are the atoms positioned? What are the properties? Give an example material.

A
  • Atoms are positioned in each corner and at each face.
  • 4 atoms per unit cell
  • Higher density than cubic or BCC ductile plastic (easy to work/deform)
  • Copper aluminum silver and gold
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64
Q

For a hexagonal close-packed (HCP) unit cell: Where are the atoms positioned? What are the properties? Give an example material.

A
  • Atoms are positioned at each vertex of the hexagon the middle of the top and bottom faces and 3 in the middle
  • 6 atms per unit cell
  • Same density as FCC bad plasticity (difficult to work/deform)
  • Cobalt cadmium zinc -titanium(different phases of some materials have different unit cells)
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65
Q

Describe what happens in metal processing and casting.

A

1) molten metal is cooled to become solid
2) solid metal is beaten/rolled to form a product

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66
Q

What are two characteristic of metal processing that can affect the mechanical properties of a metal?

A
  • Heat
  • Plastic deformation
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67
Q

Describe the arrangement of atoms in a hot vs. a cold metal

A
  • Hot: unstructured and amorphous
  • Cold: crystal much more organized
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68
Q

Describe how someone would cast metal

A

1) make a mold cast in the shape that you want the final metal
2) heat up the metal until it is liquid
3) pour the molten metal in the mold cast and wait until the metal cools and the crystal structure forms

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69
Q

Define nucleation of crystal formation

A

The time/place where the first unit cell solidifies

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70
Q

Define the growth phase of crystal formation

A

new unit cells attach to existing unit cells

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71
Q

Define grain boundaries in crystal formation

A

The places where larger crystals touch but dont attach like normal

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72
Q

What is a grain boundary

A

Def: The interference point where crystal structures meet is called the grain boundary.

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73
Q

What is a grain?

A

Crystal will grow naturally until they begin to interfere.

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74
Q

Why do grain boundaries form?

A
  • If two crystal structures are growing in two different places eventually they will grow so large that they touch.
  • If one crystal structure grows at an angle of 10 and a different crystal structure grows at an angle of 11 the atoms will not align perfectly and there will be a grain boundary
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75
Q

What are 3 consequences of grain boundaries?

A
  • Different mechanical properties
  • It can cause defects
  • There can be high interfacial energy (energy between different crystal structures)
  • The energy between grain boundaries is highr than if you go away from the grain boundary to the middle
  • This can result in corrosion especially with a lot of grain boundaries
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76
Q

What are the 3 categories of crystal defects?

A
  • Point
  • Line
  • Planar
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77
Q

List 3 types of point defects

A
  • Vacancy
  • One atom is missing
  • Nearby atoms shift
  • Substitutional
  • A different atom replaces one that should be in the lattice.
  • Larger and smaller atoms move nearby atoms in the lattice
  • Interstitial (self)
  • Atom is in the wrong location and not connected to the lattice
  • The atom pushes on nearby atoms shifting them
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78
Q

Describe what happens to a metal when stress is applied.

A

Dislocations (defects) are generated they move and the metal deforms

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79
Q

What is a self interstitial addition point defect?

A

The atom is the correct material but it’s in the wrong location

80
Q

Describe a frenkel-pair

A
  • A frankel pair is a combination of vacancy and interstitial addition point defects.
  • There is one missing atom and nearby there is one extra atom
81
Q

what is a solid solution.

A
  • Def: A metal where there is a normal crystal structure that includes impurities
  • More abundant element is solvent
  • Less abundant element is solute
82
Q

Define a metallic alloy.

A

A metal comprised of two or more elements at least one of which is metallic

83
Q

What are the two ways that alloys form?

A
  1. Substitutional
  2. Interstitial addition
84
Q

What are the 4 Hume-Rothery rules

A

1) Atoms should have similar size (15% difference in size)
2) Atoms should have similar electronegativities
3) Atoms should have similar valence charges
4) Crystal structures must be the same (e.g. BCC and BCC or FCC and FCC)

85
Q

What are the rules for an interstitial solution?

A

Solute atoms must be small so they can fit between the larger solvent atoms

86
Q

What are important interstitial solute atoms?

A
  • Carbon
  • Hydrogen
  • Boron
  • Nitrogen
  • Oxygen.
87
Q

Define diffusion

A

The movement of atoms due to thermal energy (kBT)

88
Q

How does solid state diffusion work when there is a vacancy point defect?

A

An nearby atom and a vacancy will swap positions

89
Q

How does solid state diffusion work when there is an interstitial addition point defect?

A

The small atom can move through the interstitial space to a new location

90
Q

Through diffusion, atoms can move:

a. to any location
b. to select locations, but there is a barrier to moving
c. to select locations, only if its below freezing temperatures
d. they can’t move

A

to select locations but there is a barrier to moving

91
Q

What is one barrier to solid state diffusion and why?

A
  • Steric hinderance.
  • It requires more energy to push the atom through if the nearby atoms are in the way.

Steric hinderance: slow reactions due to bulky molecules

92
Q

If there is a lot of steric hindrance during solid state diffusion is the activation energy Q high or low?

A

High

93
Q

Reducing the grain size will do what to crystal packing?

A
  • More homogeneous crystal packing
  • Impedes dislocation motion
  • Improves toughness
94
Q

What are 2 ways that grain size can be controlled?

A
  • Slowing the rate of solidification
  • Plastic deformation after it has solidified (beat it/roll it)
95
Q

Describe how adding an element to a solid solution can make it stronger.

A

It can halt a dislocation preventing it from further deforming. It increases the energy barrier to movement.

96
Q

Which is stronger: pure metal or alloys?

A

Alloy because the solute strengthens bonds and reduces defects.

97
Q

define strain hardening

A

Ductile metals become stronger after plastic deformation at low temperatures (also known as ‘cold working’)

98
Q

Explain why strain hardening occurs.

A
  • The dislocation density increases with cold working.
  • The distance between dislocations decreases.
  • Dislocations also block other dislocations.
99
Q

define annealing

A

Heating a metal to remove defects

100
Q

Explain how annealing works.

A

Diffusion is faster at high heat where dislocations can easily move to lower energy positions in the crystal structure.

101
Q

What are ceramics used for in biomaterial?

A
  • Orthopedic implants
  • Coatings and thin films
  • Bone cements
  • Scaffolds
  • Bone graft
102
Q

What is a ceramic?

A
  • Metal and nonmetal
  • Ionic bonding – non-directional (can also with covalent bonds)
  • May be crystalline think quarts SiO2 (like metals) or amorphous (glassy)

e.g. pottery, hydroxyapatite, SiO2, NaCl, TiO2

103
Q

Where does ionic bonding occur?

A
  • Occurs between + (cation) and -(anion) ions.
  • Requires e- transfer
  • Electronegativity
  • Tendency to attract e- during bound formation
  • Net charge is 0 (electroneutral)
  • Does not support deformation
104
Q

What is an example of ionic bonding?

A

NaCl

105
Q

What are the properties of ceramics?

A
  • Generally inert
  • Resists chemical reactivity (corrosion)
  • Strong (density of ceramics is less than the density of metal)
  • Sensitive to reformation (brittle)
  • Electroneutrality contributes to inertness/brittle
106
Q

What are the advantages of using ceramics?

A
  • Inert in body (or bioacticy in body); chemically inert in mant environment (unlikly to corrode)
  • High wear resistance (important in the application of orthopedics)
  • High modulus (stiffness) & compressive strength
107
Q

What are the disadvantages of using ceramics?

A
  • Brittle (low frature resistance flow tolerance (strong but when it deform it fails.))
  • Low tensile strength (fibers are exception)
  • Poorfatigue resistance (related to flaw tolerance(once a crash occures it is likely to fail))
108
Q

Cystalline ceramic
Long range order
Has structure
Orgnaized structure of grains
Glassy ceramic
Short range order
Typically do not form grains
Glass-ceramics
Some combination of systaline grains surrounded by amorphous material

do you know it?

A

do you know it?

109
Q

What is Pauling’s rules?

A
  • Magnitude of charge: ceramic crystals are neutral
  • AmXp the number required for charge neutrality
  • Eg. TiO2 m=1; p=2
  • NaCl Fe2O3
  • Relative size of the ions – Cations typically smaller
  • Cation too small to interact with all anions
  • Cation-anion can interact
110
Q

photo, crystal structure, page 15

do you know it?

A

do you know it?

111
Q

If i have a crystal structure made out of cesium ion (rc=0.170nm) and anion X- what would anion would produce the biggest coordination number?

A

F-(rc=0.133nm)

112
Q

Types of defects
Point
Vacancies
Intersititial atoms
Substitutional atoms
Line
Edge Dislocations (occurs when there is termination of a plane of atoms in a crystal)
Planar/Area
Grain boundaries
Stacking faults
Twin boundaries
Phase interface
Volume defects
Microvoids
Microcracks
Second-phase precipitates

do you know it?

A

do you know it?

113
Q

Burger’s vector and circuit
Photo page 16

do you know it?

A

do you know it?

114
Q

b burger’s vector in metals vs. ceramics

A
  • Metal
  • Malleable
  • Ductile
  • Ceramic
  • Keep charge neutral
  • Has to move farther
  • Burgers vector is bigger
115
Q

Edge dislocation is a type of:

A

Line defect

116
Q

3 types of fixation:

Morhological fixation
Dense insert nonporous ceramics attach to bone(or tissue)growth in to surface irregularities by press fitting into a defect as a type of adhesive bone
Biological fixation
Poroous inert ceramics attach by bone resulting from ingrouth(into pores) resulting in mechanical attachment of bone to material
Bioactive fixation
Dense nonporous surface-reactive ceramics attach directly by chemical boding with bone – bioactive glasses&Hydroxyapatite.

do you know it?

A

do you know it?

117
Q

Bioinert bioceramics (stable nonreactive)
carbon(grahite graphene)
Alumina
Zirconia ceramics
Advantages
Able to sustain very high mechanical loads
Very thin capsule formation
Excellent friction and wear properties occur when grains are very small.
Disadvantages
Prevent shelling of grains (wear resistance aseptic loosening)

do you know it?

A

do you know it?

118
Q

Bioactive bioceramics (direct + bone-impland bond)
Hydroxyapatite
Bioglass
A_W glass
Advantages
Gained acceptance as bone substitute
Repair of bony defects
Repair of periodontal defects

do you know it?

A

do you know it?

119
Q

bioerodible/bioresorbable (gradual degradation)
Tricalcium phosphate
Calcium sulphate

do you know it?

A

do you know it?

120
Q

photo, graph of bioactivity, page 18

A

do you know it?

121
Q

What are the 4 forces that can be applied to test materials?

A

Tension
Direction: 2 forces away from the center (think like stretching a rubber band)
Compression
Direction: 2 forces toward the center (think like squeezing juju’s duzi)
Shear
Direction: 2 forces on a surface in opposite directions
Torsion
Direction: wisting two different directions (like opening a jar)

122
Q

What does a load cell do?

A

Detects force in one direction

123
Q

What is the equation for tension/compression engineering stress?

A

σ= F / A0 [=] N / L2

124
Q

What is the equation for tension/compression engineering strain?

A

ε = ΔL / l0} [=] L / L

125
Q

What is the equation for shear stress?

A

τ = F / A0

126
Q

What is the equation for shear strain?

A

γ = tan(θ)
θ is the deformation angle

127
Q

photo, stress strain cuve, page 19

A

do you know it?

128
Q

What is the difference between elastic and plastic deformation?

A

Elastic deformation: the line is linear strain is reversible
Plastic deformation: the line is not linear strain is irreversible

129
Q

Ceramics deform at (low/high) strain and then break. Before breaking is this plastic or elastic deformation?

A

Low elastic deformation

130
Q

Does a stress-strain curve for metal have plastic deformation elastic deformation or both?

A

Both. First they elastically deform then they plastically deform.

131
Q

What are 3 properties of polymers that are shown on a stress strain curve

A
  • brittle
  • Plastic deformation
  • Elasticity
132
Q

photo, stress strain curve with colors, page 20

do you know it?

A

do you know it?

133
Q

What is the equation for elastic deofmration (hookean response)?

A

σ = Eε

134
Q

What is the equation for the shear modulus?

A

τ = Gγ

135
Q

What is the equation relating shear modulus and young’s modulus?

A

E = 2G(1+ν)

ν (nu) is poisson’s ratio. ν = 0.5 for incompressible fluids like water

136
Q

Choose: A high modulus means a (small/large) stress is required to deform material.

A

Large

137
Q

Define yield strength.

A
  • (x,y) coordinate is (εy, σy)
  • The stress and strain where plastic deformation starts to occur
138
Q

What is tensile strength M?

A

The ultimate maximum stress that the material can experience before starting to fail

139
Q

What is necking?

A

Thinning of the material

140
Q

Choose: Thermoplastics have (low/high) elongation with plastic deformation

A

high

141
Q

What is an elastomer?

A

High elongation with plastic deformation

142
Q

What is elongation?

A

% EL = (lf - l0) / l0
The distance that a material has permanently deformed

l is lowercase L

143
Q

What is the medical term for young’s modulus E (and units)?

A

Stiffness, N/m2

144
Q

What is the medical term for ultimate tensile strength sigma_max (and units)?

A

Strength, N/m2

145
Q

What is the medical term for toughness?

A

toughness

146
Q

What is the medical term for strain at rupture epsilon_max ?

A

Extensibility or stretchability

147
Q

What is the medical term for resilience (and units)?

A

Spring efficiency % units
Area under the curve in the elastic region

148
Q

What is the medical term for fatigue lifetime (and units)?

A

Durability # of cycles until it stops working

149
Q

What is the medical term for energy storage capacity W (and units)?

A

Spring capacity, J / kg

150
Q

What is creep?

A

Plastic deformation of a material under constant load over time

151
Q

Under constant load is the strain linear or nonlinear?

A

nonlinear

152
Q

What is stress relaxation?

A

Decrease in stress over time under constant strain

153
Q

Under constant strain is the load linear or nonlinear?

A

Nonlinear

154
Q

What is viscoelastic behavior?

A

cting like a viscous liquid and elastic at in different time frames (stretch raw noodles slowly compared to hit it really hard)

155
Q

In short time frames are viscoelastic materials more viscous or elastic?

A

Elastic

156
Q

What is the difference between the maxwell and the voight models of viscoelasticity?

A

Maxwell puts springs and dashpots in series
Voight puts springs and dashpots in parallel

157
Q

What is the difference between a spring and a dashpot (弹簧一黏壶模型)?

A

spring represents elastic behavior (rubber band)
A dashpot represents viscous behavior (moving your hand in a pool)

158
Q

What is the standard solid model?

A

A combination of maxwell and voigt models (series and parallel) springs and dashpots to model a system (human spine biomaterials etc.)

159
Q

Choose: Human tissues are (viscous/elastic/viscoelastic).

A

Viscoelastic. Cellular morphology and development depend on these viscoelastic properties.

160
Q

List things that can be obtained by various techniques for surface analysis.

A

Length-scales
Ease
Chemical information
Structural information

161
Q

What does contact angle measure?

A

The angle at the edge of a drop of liquid

162
Q

What is the equation for contact angle?

A

γSV - γSL - γLVcos(θ)=0

163
Q

What are the advantages of using contact angle analysis?

A

Easy and inexpensive

164
Q

What material has the highest contact angle? A. PEG B. Wax C. Teflon or D. Collagen

A

B. Wax.
PEG and Collagen are < 90°

165
Q

What are the 3 primary microscopy techniques?

A

Optical
Scanning electron microscopy (SEM)
Transmission electron microscopy (TEM)

166
Q

How does optical microscopy work?

A

Polarized light is reflected off the material

167
Q

What are the limits of optical microscopy?

A

100 nm resolution due to the wavelength of visible light.

168
Q

How does scanning electron microscopy (SEM) work?

A

Coat the material in an electron reflective metal (like gold). Shoot electrons at the materal and detect electrons and x-rays that are emitted.

169
Q

How does transmission electron microscopy (TEM) work?

A

Shoot electrons through a material and see what electrons pass through it

170
Q

What is atomic force microscopy (AFM)?

A

Rub a small needle to the surface and measure the van der waals force interactions

171
Q

What is fourier transform infra-red spectroscopy (FTIR)?

A

Measure molecule vibrations by looking at the absorption of different light.

172
Q

What vibrational modes does fourier transform infrared specrtroscopy (FTIR) measure?

A

Stretching (symmetric and asymmetric)
Deformation/bending
Rocking
Wagging
Twisting

173
Q

What are two common bonds shown by fourier transform infrared specrtroscopy (FTIR)?

A

C-H stretching near wavenumber 2900
C=O near wavenumber 1750

174
Q

What is mass spectroscopy?

A

Shoot electrons at the sample to ionize it detect the mass of particles that are emitted from the sample

175
Q

What is different between normal and secondary ion mass spectroscopy (SIMS)?

A

SIMS shoots ions (O2+, Ar+, etc.) to release ions from the material, which are recorded.
Normal MS directly breaks off charged fragments of the material

176
Q

What is matrix assisted laser desorption ionization (MALDI) mass spectroscopy?

A

A laser releases material from the surface (desorption) that is bonded to small molecules that can be ionized

177
Q

What is apoptosis?

A

Cell death that is programmed intentional and controlled.

178
Q

What is necrosis?

A

Cell death that is chaotic. The membrane will break down and the cell insides will be released.

179
Q

What is a scratch assay?

A

Scratch a cell and then measure it’s ability to heal the wound

180
Q

Which is greater: elastic modulus E for compression or tension (for non-fiber materials)?

A

Compression

181
Q

What are 5 different operations that cells can do?

A

Divide/differentiate
Metabolize
Migrate
Secrete biologic materials
Rearrange their internal and external environments

182
Q

What are 4 types of biological testing and what do they mean?

A

In-vivo → in a living body
In-vitro → in glass in a lab
Ex-vivo → in a sample taken from a living body
In-silico → in a computer simulation

183
Q

What is an MTT assay?

A

It measures reduction and mitochondrial activity.

184
Q

How does an MTT assay work?

A

Yellow MTT is reduced to become purple Formazan due to reductase from the mitochondria
A darker purple means more reduction and that the cell is working good (good vitality)

185
Q

What is one thing that can’t be measured by an MTT assay

A

Cell proliferation

186
Q

What does an alamar blue assay measure and how does it do it?

A

Measures cell viability and proliferation
Non-fluorescent dye is converted to fluorescent red dye by reduction reactions
More fluorescence means more living cells

187
Q

What is a Live/Dead Assay and how does it work?

A

Shows living and dead cells
Live cells are green dead cells are red
Dead cells are red because EthD-1 can only enter dead cells and bind to DNA there

188
Q

What are the limitations of a live/dead assay?

A

You can count the cells but it’s not accurate
Can’t continue to culture cells after assay

189
Q

What number is output from a live/dead assay?

A

% viability= [# green / (#green + # red)] * 100%

190
Q

What is a BrdU Assay?

A

Measures cell division
BrdU is a synthetic chemical similar to thymidine that is added to a cell’s DNA during cell division which reduces the amount of BrdU that is leftover.

191
Q

G (stiffness) is proportional to Nx (# of crosslinks) is proportional to Keq

A

do you know it?

192
Q

T1/2 is proportional to 1/k-1

A

do you know it?

193
Q

Hydrogels aim to be the same complexity as native human matrices

A

do you know it?

194
Q

Hydrogels can serve as in vitro models

A

do you know it?

195
Q

Hydrogels are useful for stem cell expansion and transplantation

A

do you know it?

BIM 109 (3 decks)

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