1.) 3D Printing (Additive Manufacturing) Flashcards
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
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
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)
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)
Describe the working mechanism for Selective Laser Sintering (SLS).
- ) Roller pushes out an even layer of powder to platform
- ) Laser beam scanned across at pre-determined positions to fuse powders together - forming layer
- ) Stage/fabrication piston is lowered and a second layer of powder is laid
- ) Process repeated to form 3D structure
What raw materials are compatible with SLS and traditional 3D printing?
- Metal
- Polymer
- Ceramic
Describe the working mechanism for 3D printing.
- ) Roller pushes out an even layer of powder to platform
- ) Binder is jetted down onto selective positions to fuse powders together
- ) Stage is lowered, second layer of powder laid.
- ) Process repeated to form 3D structure.
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)
Describe the working mechanism for Inkjet printing.
- ) Piezoelectric actuator generates a picolitre drop upon receiving current (volume of piezoelectric material shrinks with current to squeeze out drop)
- ) Drop ejects and reaches a substrate at pre-determined positions
- ) Ejected drop solidifies under UV exposure
- ) Repeat cycle to form 3D structure.
- Used in electronics
Describe the working mechanism for Stereolithography. What is its significance?
AKA ‘3D-Photons’
- ) UV laser is scanned across a layer of photopolymerisable monomers at pre-determined positions
- ) Monomers polymerise and solidify under UV; stage is then moved up to allow another layer of monomers to fill the space
- ) 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)
What do Inkjet printing and Stereolithography have in common?
Use the same raw materials:
- Photopolymerisable monomers
Describe the working mechanism for Fused Deposition Modelling. What is its significance?
- ) Feed polymer into heater
- ) Melt polymer (to molten state)
- ) Extrude polymer through a nozzle while stage is moved in XYZ axis according to 3D structure being printed
- ) Extruded polymer strand cools and solidifies to form 3D structure
- Cheapest form of 3D printing
- Early technology (1990s)
What are thermoplastic materials? Examples?
Materials that soften and become mouldable upon heating, hardening upon cooling.
E.g.:
- Polyetherether ketone (PEEK)
- Polycaprolactone
- Polylactic acid
What are the printable materials used in Fused Deposition Modelling?
Thermoplastic polymers
What conditions commonly seen in 3D printing prevent their use in printing cells?
- ) High temperature: Fused Deposition Modelling and SLS
- ) Long UV exposure time: stereolithography (cells can’t be exposed for prolonged time)
- ) 3D printing: toxic binders
What are the 3D Bio-printing Subtypes availible?
- Inkjet printing
- Laser assisted printing
- Extrusion bioprinting (microextrusion)
Describe the working mechanism of Inkjet printing WRT 3D Bioprinting
- ) Piezoelectric/thermal actuator generates a picolitre drop upon receiving current (volume of piezoelectric material shrinks with current to squeeze out drop)
- ) Drop ejects and reaches a substrate at pre-determined positions
- ) Ejected drop solidifies
- ) 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
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
Describe the working mechanism of Laser assisted printing.
- ) Laser beam shines on energy absorbing layer at pre-determined positions (3-layer raw material)
- ) 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.
Describe the working mechanism of Extrusion bioprinting.
Similar process to Fused Deposition Modelling (w/o the high temperatures)
- ) Hydrogel/hydrogel + cell mixture with suitable viscosity range is loaded in a cartridge
- ) Material is extruded through a nozzle by pressure or mechanical forces, whilst stage is moved in XYZ axis
- ) Extruded hydrogel strand forms 3D structure.
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)
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)
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)
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
