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#FME - Nanotechnology and Advanced Materials > 1.) 3D Printing (Additive Manufacturing) > Flashcards

1.) 3D Printing (Additive Manufacturing) Flashcards

1
Q

Outline the general 3D printing (Additive Manufacturing) process.

A

3D Model is generated:

  • MRI/X-ray/CT
  • Design software (CAD)
  • Combination of both

Printer software slices virtual model into many layers:

  • Software determines thickness of slices
  • Thinner layers = higher quality

3D printing process:

  • Layer-by-layer
  • From bottom to top
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2
Q

How does 3D Printing (Additive Manufacturing) compare to Subtractive Manufacturing (Traditional)?

Advantages of the former?

A

Advantages of 3D Printing (Additive):

  • Complex structures can be created in a limited timeframe
  • Complex structures are difficult/impossible to make using traditional, Subtractive manufacturing (complex geometry)
  • Layer by layer build-up w/Additive Manufacturing overcomes this
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3
Q

What range of technologies fall under 3D Printing/Additive Manufacturing?

A

It is an umbrella term for:

  • Sterolithography
  • Fused deposition modelling
  • Inkjet printing
  • 3D printing
  • Laser selective sintering
  • Bioprinting (3D Bioprinting; involving cells)
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4
Q

Name examples of 3D printed medical devices.

A
  • Surgical guide for orthopaedic surgeries (aligning pins to drill holes etc)
  • 3D printed implant (e.g. splint to help keep airways open of newborn)
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5
Q

Describe the working mechanism for Selective Laser Sintering (SLS).

A
  1. ) Roller pushes out an even layer of powder to platform
  2. ) Laser beam scanned across at pre-determined positions to fuse powders together - forming layer
  3. ) Stage/fabrication piston is lowered and a second layer of powder is laid
  4. ) Process repeated to form 3D structure
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6
Q

What raw materials are compatible with SLS and traditional 3D printing?

A
  • Metal
  • Polymer
  • Ceramic
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7
Q

Describe the working mechanism for 3D printing.

A
  1. ) Roller pushes out an even layer of powder to platform
  2. ) Binder is jetted down onto selective positions to fuse powders together
  3. ) Stage is lowered, second layer of powder laid.
  4. ) Process repeated to form 3D structure.
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8
Q

SLS and 3D printing are similar in many ways; how do they differ? What considerations are there with the latter?

A
  • In 3D printing, binder is used to bind powders/raw material together instead of laser beam in SLS.
  • 3D printed structure from traditional 3D printing is often heated in an oven after binding; increase mechanical strength of structure (binder often not strong enough on its own)
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9
Q

Describe the working mechanism for Inkjet printing.

A
  1. ) Piezoelectric actuator generates a picolitre drop upon receiving current (volume of piezoelectric material shrinks with current to squeeze out drop)
  2. ) Drop ejects and reaches a substrate at pre-determined positions
  3. ) Ejected drop solidifies under UV exposure
  4. ) Repeat cycle to form 3D structure.
  • Used in electronics
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10
Q

Describe the working mechanism for Stereolithography. What is its significance?

A

AKA ‘3D-Photons’

  1. ) UV laser is scanned across a layer of photopolymerisable monomers at pre-determined positions
  2. ) Monomers polymerise and solidify under UV; stage is then moved up to allow another layer of monomers to fill the space
  3. ) Process repeated to form 3D structure.
  • First type of 3D printing (1980s)
  • Forms 3D object ‘upside down’ - sample platform moves up one layer at a time after UV exposure of each layer (for photo-crosslinking)
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11
Q

What do Inkjet printing and Stereolithography have in common?

A

Use the same raw materials:

- Photopolymerisable monomers

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12
Q

Describe the working mechanism for Fused Deposition Modelling. What is its significance?

A
  1. ) Feed polymer into heater
  2. ) Melt polymer (to molten state)
  3. ) Extrude polymer through a nozzle while stage is moved in XYZ axis according to 3D structure being printed
  4. ) Extruded polymer strand cools and solidifies to form 3D structure
  • Cheapest form of 3D printing
  • Early technology (1990s)
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13
Q

What are thermoplastic materials? Examples?

A

Materials that soften and become mouldable upon heating, hardening upon cooling.

E.g.:

  • Polyetherether ketone (PEEK)
  • Polycaprolactone
  • Polylactic acid
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14
Q

What are the printable materials used in Fused Deposition Modelling?

A

Thermoplastic polymers

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15
Q

What conditions commonly seen in 3D printing prevent their use in printing cells?

A
  1. ) High temperature: Fused Deposition Modelling and SLS
  2. ) Long UV exposure time: stereolithography (cells can’t be exposed for prolonged time)
  3. ) 3D printing: toxic binders
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16
Q

What are the 3D Bio-printing Subtypes availible?

A
  • Inkjet printing
  • Laser assisted printing
  • Extrusion bioprinting (microextrusion)
17
Q

Describe the working mechanism of Inkjet printing WRT 3D Bioprinting

A
  1. ) Piezoelectric/thermal actuator generates a picolitre drop upon receiving current (volume of piezoelectric material shrinks with current to squeeze out drop)
  2. ) Drop ejects and reaches a substrate at pre-determined positions
  3. ) Ejected drop solidifies
  4. ) Repeat cycle to form 3D structure.
  • Some cells are photo-compatible; provided they are not exposed for too long
  • Balance of controlling exposure time to cure monomer vs. killing cells
18
Q

What printable material do two of three Bio-printing subtypes share?

A

Cell suspension (Inkjet + Laser assisted):

  • ‘Bio-ink’
  • Cells are suspended in cell culture media
19
Q

Describe the working mechanism of Laser assisted printing.

A
  1. ) Laser beam shines on energy absorbing layer at pre-determined positions (3-layer raw material)
  2. ) As a result, a shockwave is generated resulting in an ejection of a drop which reaches a substrate

> > > Generating rop of cell suspension differs to Inkjet Printing.

20
Q

Describe the working mechanism of Extrusion bioprinting.

A

Similar process to Fused Deposition Modelling (w/o the high temperatures)

  1. ) Hydrogel/hydrogel + cell mixture with suitable viscosity range is loaded in a cartridge
  2. ) Material is extruded through a nozzle by pressure or mechanical forces, whilst stage is moved in XYZ axis
  3. ) Extruded hydrogel strand forms 3D structure.
21
Q

How does Extrusion bioprinting differ mainly WRT to Inkjet and Laser assisted bioprinting?

A

The printable materials:
- Hydrogels or hydrogel/cell mixtures that have a suitable viscosity range
(toothpaste-like texture)

22
Q

What is a hydrogel?

A
  • Non-fluidic colloidal networks/polymer networks physically or chemically crosslinked containing a large amount of water
  • Similar to extracellular matrix environment (proteins/sugars/water)
    E.g. Alginate (derived from algae in sea)
23
Q

What is the ideal viscosity for a hydrogel to be used in Extrusion printing?

A
  • Similar to creams/toothpaste
  • Should be able to maintain own weight and stay in its 3D shape outside of original container (unlike viscosity of shower gels etc)
24
Q

Describe the two different flow behaviours.

A

Newtonian:

  • Like water
  • Viscosity does not change w/shear rate (how quickly something is deformed)

Shear-Thinning (most hydrogels):

  • Viscosity decreases w/shear rate
  • Most creams etc.: smearing cream on skin quickly results in lesser viscosity and greater ease of spreading
25
Q

How is viscosity quantified?

A

Using a rheometer:

  • Measures force required to rotate upper plate against lower plate which contains the hydrogel
  • A greater rotational speed of the plate = greater shear rate (deforming something more quickly)
26
Q

Why are 3D printed medical devices classed as ‘custom made medical devices’? What does this mean?

A
  • Each device is unique (to the patient)
  • Thus impossible to sample devices during QC; there is no control
  • THUS manufacturing process must implement the appropriate quality requirements
  • Translated into a legal requirement imposed on manufacturers of 3D-printed, patient specific medical devices
    »> Lots of QC includes destruction/stress testing (not possible if custom 3D device to go into patient)

#FME - Nanotechnology and Advanced Materials (3 decks)

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