1.) 3D Printing (Additive Manufacturing) Flashcards Preview

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Flashcards in 1.) 3D Printing (Additive Manufacturing) Deck (26)
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1

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

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

2

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

Advantages of the former?

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

3

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

It is an umbrella term for:
- Sterolithography
- Fused deposition modelling
- Inkjet printing
- 3D printing
- Laser selective sintering
- Bioprinting (3D Bioprinting; involving cells)

4

Name examples of 3D printed medical devices.

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

5

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

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

6

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

- Metal
- Polymer
- Ceramic

7

Describe the working mechanism for 3D printing.

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.

8

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

- 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)

9

Describe the working mechanism for Inkjet printing.

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

10

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

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)

11

What do Inkjet printing and Stereolithography have in common?

Use the same raw materials:
- Photopolymerisable monomers

12

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

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)

13

What are thermoplastic materials? Examples?

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

E.g.:
- Polyetherether ketone (PEEK)
- Polycaprolactone
- Polylactic acid

14

What are the printable materials used in Fused Deposition Modelling?

Thermoplastic polymers

15

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

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

16

What are the 3D Bio-printing Subtypes availible?

- Inkjet printing
- Laser assisted printing
- Extrusion bioprinting (microextrusion)

17

Describe the working mechanism of Inkjet printing WRT 3D Bioprinting

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

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

Cell suspension (Inkjet + Laser assisted):
- 'Bio-ink'
- Cells are suspended in cell culture media

19

Describe the working mechanism of Laser assisted printing.

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

Describe the working mechanism of Extrusion bioprinting.

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

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

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

22

What is a hydrogel?

- 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

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

- 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

Describe the two different flow behaviours.

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

How is viscosity quantified?

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

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

- 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)