3D Printing: Types, Materials, and Fundamentals

3D Printing Fundamentals

• 3D printing is also known as Additive Manufacturing, which involves creating objects by adding materials layer by layer.
• The concept dates back to the 1980s.

Growing Interest in 3D Printing

• The cost of the technology has decreased rapidly in the last 10 years.
• 3D printers are available from less than £99.
• There are thousands of different types of 3D printers available.

3D Printer Types

• Material Extrusion: Fused Deposition Modeling (FDM) or Fused Filament Fabrication (FFF)
• Solid-Liquid-Solid
• VAT Polymerisation: SLA / DLP
• Liquid-Solid
• Powder Bed Fusion-SLS
• Solid-Liquid-Solid

Printing Materials

• Hard materials: PLA, ABS, nylon, acrylic, metals, concrete
• Soft materials: TPU, silicone, clay
• Organic materials: chocolate, icing, cellular
• There are over 50 different types of materials available.

Layer and Resolution Details

• Layer thickness is about 100 microns.
• In-plane resolution is 100 microns.
• The speed of printing varies from 10 minutes to days, based on the object size

3D Printing Pipeline

• The 3D printing pipeline includes various steps, starting with source data from CAD, surface scans, or medical imaging.
• This data is then processed through slicing to create a 3D file, which is converted into a GCODE file.
• The 3D printer then uses the GCODE file to produce the 3D print

3D Printing Applications at King's Health Partners (KHP)

• KHP utilizes 3D printing facilities for routine clinical applications, research (medical devices, anthropomorphic phantoms, implants), and education (additive manufacturing modules for engineering and healthcare students).
• The Medical Physics Department at KHP has a dedicated 3D Printing Centre that produces 3D printed models for clinical service and research.
• Clinical services include cardiac models for surgical planning in patients with congenital heart disease (CHD).

Anthropomorphic Phantoms in Research

• Anthropomorphic phantoms can be used for testing novel medical devices.
• They help generate synthetic medical images for training AI algorithms.
• These are used for surgical procedure simulation for training and rehearsal, and to validate biophysical modelling algorithms.
• The use of phantoms reduces the need for patient data, animal experiments, cadaver experiments, and overall costs

Valve Models

• Valve models can be created using two-part molds and silicone

Direct Silicone Printing of Valve Models

• Direct silicone printing of valve models is performed using custom silicone printers, based on open-source designs.
• This method reduces manufacturing time and costs, and increases the available build volume

Applications in Lung Cancer Surgery

• Used for lung cancer surgery involving patients with bone involvement, 3D printing technology is used to create low-cost PLA prints and silicone molds for implants.
• 15+ patients have received implants so far with no complications.
• Benefits include improved respiratory mechanics and aesthetics.
• This represents a lower cost alternative than titanium implants.

3D Bioprinting

• 3D bioprinting involves using living components to print tissues and organs.
• 3D Bioprinting creates 3D scaffolds and seeds them with cells or to print bio-inks comprised of cells + scaffold (usually a hydrogel).

Impact and Ethical Considerations

• 3D printing technologies are already used in medical devices, surgical planning, implants, and research.
• Printing tissues and organs is challenging, but progress is rapid; there are ethical issues to consider.
• 3d-printing is considered a booming research area and can be useful for research and testing of drugs/devices and implants.

3D Bioprinting Workflow

• 3D bioprinting starts with preprocessing, including imaging (X-ray, MRI, CT, ultrasound) and 3D modelling & slicing.
• Processing includes bioink preparation where patient cells are harvested, cultured and prepared into cells-laden bioink in preparation for use in a 3D bioprinter.
• After the bioprinting stage, the tissues undergo post-processing. This may involve bioreactors for tissue maturation.
• Bioprinted structures can then be for disease modelling, drug/cosmetic testing, or transplanted into patients.

Bioprinting Examples

• Examples of skin bioprinting include human skin with epidermis, DEJ (Dermoepidermal junction) and Dermis, bioink with Fibroblasts + Keratinocytes, and 3D Bioprinted skin
• Examples of heart muscle bioprinting include a bioink with myocytes, functional patch of myocardium