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Biomaterials > Week 13 > Flashcards

Week 13 Flashcards

1
Q

What does the bulk of biomaterial govern?

A

mechanical integrity or “failure”

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2
Q

What does the surface of biomaterials govern?

A

cell-biomaterial interactions within a depth of < 1 nm

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3
Q

What is the purpose of surface modification?

A

to alter surface properties to enhance performance in biological environment while retaining bulk properties of biomaterial/device

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4
Q

What are the 6 biomaterial surface interactions?

A
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5
Q

What are the 6 objectives of surface functionalization?

A
  1. clean a surface
  2. reduce/eliminate protein adsorption
  3. reduce/eliminate cell adhesion (pathogens)
  4. promote cell attachment/adhesion
  5. increase hardness (stiffness)
  6. enhance corrosion/degradation resistance
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6
Q

What are the two types of surface modification approaches?

A
  1. subtractive modification (physical method)
  2. additive modification (chemical method)
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7
Q

What is subtractive modification?

A

removal of surface layer via
- abrasive blasting
- plasma treatments

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8
Q

What is additive modification?

A

depositing films or biological factors via
- physical and chemical vapor deposition
- grafting
- attachment of self-assembly molecules
- layer-by-layer deposition

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9
Q

preparing biomaterial surfaces for further treatment, cleaning or finishing

A

abrasive blasting

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10
Q

Abrasive blasting is performed to do what 3 things?

A
  1. remove surface contaminants
  2. roughen implant surfaces to increase surface area
  3. improve the adhesion of coatings on implant surfaces
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11
Q

Is high roughness good or bad for bacteria and infection?

A

good for bacteria
bad for infection

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12
Q

Describe the stent surface before and after abrasive blasting

A

after fabrication
- surface quality has lots of scratches and inconsistencies

after sand blasting
- roughness is even

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13
Q

What 4 things is surface roughness influenced by?

A
  1. type of abrasive media (“powder”)
    - sodium bicarbonate
    - glass (SiO2)
    - alumina
    - CaP
  2. size/shape of abrasive media
  3. gas or air pressure
  4. nozzle to substrate distance
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14
Q

How does abrasive blasting affect the wettability of a surface?

A

adding surface roughness makes a surface go from hydrophilic –> superhydrophilic

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15
Q

What are the 3 advantages of increased surface roughness?

A

bone-implant interaction:
- increase surface area of the biomaterial adjacent to tissue
- improved bone-type cell attachment
- increased bone present at the implant surface

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16
Q

What are the disadvantages of increased surface roughness?

A

bacteria/pathogen –> if you have rough surfaces its going to be hard to remove the bacteria/pathogen

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17
Q

What two types of surface alteration is plasma glow discharge used for?

A
  1. chemical
  2. physical
18
Q

What is plasma glow discharge strongly dependent on?

A

process parameters

19
Q

What is plasma glow discharge frequently used for?

A
  1. cleaning
  2. preparation
  3. modification
20
Q

an atom/molecule acquires a negative or positive charge by gaining or losing electons

A

ionization

21
Q

Describe direct current glow discharge

A
22
Q

Describe what happens during surface modification from direct current glow discharge

A

by forcing the electrons to come out, and go towards the material surface, you can create a specific plasma that can:
- etch surface
- add functional groups
- change chemistry of the material

**utilizing electrical field –> create ions –> forced to heat and strike the material –> change material properties

23
Q

What is the plasma outcome?

A

before plasma, contact angle is larger
after plasma, contact angle is smaller

24
Q

What is the plasma outcome for chemical modification?

A

change the chemistry of the surface

25
Q

What is the plasma outcome for antibacterial?

A
26
Q

This method involves depositing hydroxyapatite on implants and is the common commercial and accepted method for dental implants

A

thermal spraying

27
Q

Describe the thermal spray process

A
  • Processes in which melted (or heated) materials aresprayed onto a surface
  • the “feedstock” (coating precursor) is heated by electrical (plasma or arc) or chemical means (combustion flame)
  • can provide coatings of 30-150 μm thick
  • powder is fed into the plasma flame through a feed and is propelled to the implant surface as semi-molten particles
28
Q

Describe the plasma spray diagram

A

plasma spray particles are on top of the material (black surface) which can change the properties of a material (i.e., make the surface more rough)

29
Q

What 7 things determine coating properties?

A
30
Q

a deposition method to produce solid materials under vacuum

A

chemical vapor deposition (CVD)

31
Q

CVD is a chemical process using temperature to _____ and drive the _____

A

heat up the gases
deposition raction

32
Q

What happens to the gas reactants during chemical vapor deposition?

A

they absorb and react with substrate surface

33
Q

What is the result of chemical vapor deposition?

A

film on the surface

34
Q

This method deposits thin films on substrates

A

physical vapor deposition (PVD)

35
Q

What are the 4 steps involved in physical vapor deposition (PVD)?

A
  1. evaporation
  2. transportation
  3. reaction
  4. deposition
36
Q

What are the 3 different types of CVD?

A
37
Q

What are the two most common PVD processes?

A
  1. sputtering
  2. evaporation
38
Q

What happens during PVD?

A

heat the metal –> release metal molecules –> metal molecules strike the item to be plated (biomaterial)

39
Q

Describe evaporation deposition

A
40
Q

relates to the tendency of particles to escape from the liquid (or a solid)

A

vapor pressure

41
Q

Describe sputtering deposition

A
42
Q

What is electrophoretic deposition?

A

Biomaterials (10 decks)

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