Material Selection Guides for 3D Printing in Medical


Choosing the right material is the first step to success in 3D printing. This guide covers the most popular 3D printing materials in medical industry, their advantages, limitations and applications, and provides a framework that help you choose the right one for your project.


select the best material for 3d printing

Credit: Tom Claes on Unsplash



Table of Contents

1. How medical 3D printing works?

2. 5 types of 3D printing technologies

3. Material selection criteria – By Applications, By Functionality

4. Typical 3D printing materials in medical field



How medical 3D printing works?


Over the past decade, medical 3D printing applications increased significantly in both clinical and research-based healthcare activities.


3D printing, also known as additive manufacturing (AM), is a process of constructing physical objects from a digital 3D model. In clinical settings, 3D printing has been well utilized to create anatomical models of body parts or organs of an individual. The 3D models enable surgeons to visualize, practice and then perform reconstructive surgery while saving time and increasing precision. Medical 3D printing also offers an economic solution for producing tailormade implants, prostheses and surgical tools due to its capacity for prototyping.


Related article: 7 Stunning Use Cases For 3D Printing In Medical Field



5 Common Types of 3D Printing Technologies


Fused Deposition Modeling (FDM)


schematic of fdm 3d printing

A diagram illustrating FDM 3D printing process. Credit: Obsessively Geek 3D Printing


Fused deposition modeling (FDM), also known as fused filament fabrication (FFF), is one of the most widely used types of 3D printing due to its simplicity and cost-efficiency. FDM 3D printers work by melting the thermoplastic filaments (such as ABS and PLA) through a heated nozzle, and then applying layer-by-layer until the object is complete. While FDM is user-friendly, it may not be the best option for printing very high quality and detailed products.


Stereolithography (SLA)


Video demonstrating SLA 3D printing process. Credit: Formlabs on Youtube


SLA (Stereolithography) 3D printing is becoming more and more popular due to its ability to produce high-accuracy, isotropic, and watertight prototypes and parts in a range of advanced materials such as ceramics and nanoparticles.


SLA uses UV lasers as a light source to cure photosensitive liquid resins into harden plastic. Due to the high precision of lasers and lasers systems, SLA printed objects have the highest resolution and accuracy, the clearest details, and the smoothest surface among the plastic 3D printing technologies.


SLA resin formulations also offer a wide range of properties as thermoplastics, however, the finished products are more fragile compared to FDM and SLS technology. Besides, the printing process of SLA is much more time consuming than FDM.


Selective Laser Sintering (SLS)


Video demonstrating how SLS 3D printing works. Credit: Protolabs on Youtube


Selective Laser Sintering (SLS) uses a high-power laser to sinter small particles of polymer powder, fusing them to build a solid structure. The materials used in SLS are thermoplastic polymers that come in a granular form.


SLS is a great solution for the rapid prototyping of functional polymers because it offers a very high degree of design freedom and high accuracy. Unlike FDM or SLA 3D printing techniques, SLS produces parts with consistent mechanical properties, meaning the produced parts are very close to end-use quality without the need of post-processing. Although there are many advantages of using SLS, there are also some disadvantages like material recycling is impossible, products are relatively brittle, and the variety of raw material is limited.


Metal 3D printing


ExOne Metal 3D Printing Process. Source: ExOne on Youtube


Metal 3D printing technique combines the design flexibility of 3D printing with the mechanical properties of metal. Selective laser melting (SLM) and direct metal laser sintering (DMLS) are two common metal additive manufacturing processes.


Metal printed parts have higher strength and hardness and are often more flexible than parts that are manufactured using traditional methods.


Support structures are always required in metal printing, due to the extreme high processing temperature and objects are usually built using a lattice pattern. Compared to thermoplastic printing processes, metal 3D printing has unique set of design rules and requires higher set-up and material cost.


Bio-printing


schematic of bio-printing

Schematic of 3D bio-printing. Source: Biopharma PEG


Bio-printing is an extension of traditional 3D printing – it prints with a mixture of living cells and biomaterials, also known as bio-inks, to create organ-like structures that let living cells multiply. The starting models can come from anywhere, a CT or MRI scan, a computer-aided design (CAD) program, or a file downloaded from the internet. Bio-printing is a pretty new technology, and it has huge potential to benefit various medical and tissue engineering fields.


Compared with other 3D printing techniques, bio-printing leads to additional complexities, such as the choice of materials, cell types, growth and differentiation factors, and technical challenges related to the sensitivities of living cells and the construction of tissues. Disadvantages include unprecise droplet size and placement and long production time.


3d-printing-technologies-comparison-table-fdm-sls-sla-metal-bioprinting


Material Selection Criteria


There are so many 3D printing materials with different properties in the market. To choose the one that is most suitable to your project, you should define your project purpose and identify your material requirements.


Two flow charts are shown below to help you select your desirable material.


Selecting a material by application


flowchart to select a 3d printing material by medical application

Selecting a material by functionality


flowchart to select a 3d printing material by functionality

Followings are more detailed material properties you may consider when choosing the right 3D printing materials:


recommendation of 3d printing materials based on material properties

Source: Formlab, IJSRP, Conserve Energy Future, ScienceDirect, Wiki, ResearchGate, Fabbaloo, Reading Plastic



Typical 3D Printing Materials in Medical Field


Polylactic acid (PLA)


PLA printed orthopedic screws, pins and plates

FDM printed PLA orthopedic screws, pins and plates. Credit: ResearchGate


PLA is one of the most popular FDM 3D printing material. It is relatively inexpensive, easy to print and biodegradable. During the worldwide pandemic of COVID-19, a group of engineers created working ventilators using PLA plastic, a 3D printer and some off-the-shelf components for hospitals treating Coronavirus patients.


3DP Technology: FDM

Price: USD 25/kg


Pros

  • Low cost

  • Easy to print

  • Rigid, stiff and good strength

  • Biodegradable

  • Odorless

Cons

  • Low heat and chemical resistance

  • Less durable than ABS or PETG

  • Not suitable for outdoor (sunlight exposure)

Applications

  • Personalized prostheses, such as limb sockets

  • Biodegradable orthopedic devices, such as screws and fixation pins, plates, and suture anchors

  • Bone scaffolds

  • Drug delivery system


Acrylonitrile butadiene styrene (ABS)


abs printed skull

FDM printed ABS skull. Credit: Sratasys


ABS is another commonly used 3D printing material to date. It is strong, lightweight and allows for easy post-processing. ABS can be melted to form liquid and cooled to form solid, and this process can be repeated many times without any significant degradation in its properties.


However, ABS is slightly more difficult to print – it is prone to warping without an enclosed and heated build chamber. Also, ABS may have odors that could be uncomfortable or irritating for users. Printing shall thus be performed in a well-ventilated area and/or with an enclosure.


3DP Technology: FDM

Price: USD 20 – 35/kg


Pros

  • Low cost

  • Tough, durable and light

  • Good heat resistance

Cons

  • Heavy warping

  • Requires heated bed or heated chamber

  • Parts tend to shrink leading to dimensional inaccuracy

  • Releases smelly and toxic chemicals during printing

Applications

  • Surgical planning models

  • Personalized prostheses

  • Orthopaedic corset


Polyether ether ketone (PEEK)


PEEK printed implant

3D printed PEEK implants. Credit: 3Dnatives


PEEK (Polyetheretherketone) is considered as one of the world’s highest performing engineering thermoplastics, offering exceptional chemical resistance and excellent mechanical properties. It is often used to replace certain metals. Since PEEK is sterilizable, it can be used for a number of medical applications including custom-made implants and medical devices.


PEEK is available in filament form for all FDM/FFF machines, and is slowly becoming available in powder form for SLS processes. It is the ideal choice for low-volume production and specialist designs where it is difficult to create prototypes using metal and traditional techniques.


3DP Technology: FDM/ SLS

Price: USD 300 – 750/kg


Pros

  • High impact strength and durability

  • Superior heat, water and chemical resistance

  • Greater design freedom

  • Biocompatible

  • Facilitate osteointegration, i.e.: bone ingrowth into an artificial implant

  • Shares similar properties to human bone

Cons

  • Requires very high printing temperatures

  • Expensive

  • Requires measures against warping

Applications

  • Customized medical devices

  • Orthopedic implants


Polyetherketoneketone (PEKK)


PEKK printed cranial implant

Customized 3D printed PEKK cranial device. Credit: Oxford Performance Materials


Belonging to the same PAEK family as PEEK, PEKK has superior machinal, thermal, and chemical properties. Thanks to its lower crystallization rate, PEKK is easier to print than PEEK.


PEKK is mainly found in filament form for high temperature FDM printers, but also in powder form for a very limited number of SLS 3D printers.


3DP Technology: FDM/ SLS

Price: USD 80 – 180/kg


Pros

  • Excellent thermal, chemical and wear resistance

  • Easier to print than PEEK, less wrapping phenomenon

  • Better antibacterial properties than PEKK

  • Does not give out toxic fumes at high temperature

Cons

  • Expensive

  • Requires very high printing temperature

Applications

  • Customized medical devices

  • Orthopedic implants


Polycarbonate (PC)

PC printed screw

FDM printed PC screws. Credit: Plastics Technology


PC is extremely strong and resists deforming at higher temperatures unlike other common 3D printer filaments. PC can be sterilized with various standard processes making it ideal for end-use parts and functional prototypes in the medical industries. However, the 3D printing of PC is more difficult since it requires higher printing temperature than other standard FDM plastics (such as ABS and PLA).


3DP Technology: FDM

Price: USD 30 – 50/kg


Pros

  • Some of the best impact and thermal resistance of any common FDM plastics

  • High transparency

  • Bendable without breaking

Cons

  • Require high printing temperature

  • Prone to warping

  • Absorb moisture from the air which can cause defects

Applications

  • Medical equipment parts


Polymethyl methacrylate (PMMA)


PMMA printed human finger bones by novus using FDM 3d printer

PMMA finger bones printed with FDM printer.


PMMA, also known as acrylic, is a strong, durable and transparent thermoplastic. PMMA has good impact strength, significantly higher than glass, but lower than some stronger and more expensive materials like polycarbonate (PC). It is applied as a PC substitute when extremely high impact isn’t necessary, but cost is issue. Besides, PMMA is extremely biocompatible with human tissue and has a long history of use in dentures, bone implants and more.


Biotech companies such as Ossfila is working on the development of PMMA-based bioactive filaments, which offers bone-like properties and accelerates implant-to-bone integration in a more affordable option.


3DP Technology: FDM

Price: USD 35 – 150/kg


Pros

  • Strong, lightweight, durable

  • High impact resistant and tensile strength;

  • Transparent

  • Inert, biocompatible

  • Affordable

Cons

  • Require high printing temperature

  • May have odors that could be uncomfortable or irritating for users

Applications

  • Surgical guides and tools

  • Orthopedic implants


Bioceramics


ceramic printed skull

SLA printed ceramic skull. Credit: 3DCream


Bioceramics are ceramic materials that are used to repair or replace damaged hard tissues like bone and teeth. The two most bioceramics explored within ceramic 3D printing are hydroxyapatite (HA) and tri-calcium phosphate (TCP). They are popular not only for their similarity to natural bone tissue but their prevalence within medicine. Extensive amount of research on bioceramics 3D printing over the past 10 years highlighted its wide range of applications and potentials in bone tissue engineering. While a lot of applications can be accomplished in 3D printing of bioceramics, the development is still in its emerging stage.


3DP Technology: FDM/ SLA

Price: USD 28 to 668/kg


Pros

  • Good mechanical properties

  • Minimal risk of rejection

  • Osteoconductitve, induces bone growth on a surface

Cons

  • Require high printing temperature

  • Shrinkage may happen during heat treatment

Applications

  • Medical devices

  • Bone scaffolds

  • Bone substitutes, such as intervertebral cages and tibial osteotomy wedges

  • Cranial or jawbone implants


Titanium


titanium printed joint implants

3D metal printed titanium joint implants using DMLS techniques. Credit: RapidMade


Titanium has become one of the most commonly used metals in 3D printing, widely employed in aerospace, joint replacements and surgical tools, electronics, and other high-performance products. In the medical industry, 3D printed titanium implants including spine, hip, knee, and extremity applications are widely applied due to the metal’s inherent biocompatibility and good mechanical properties.


3DP Technology: Metal 3D printing

Price: USD 300 – 600/kg


Pros

  • High mechanical strength

  • Good corrosion resistance

  • Biocompatible

Cons

  • Expensive

  • Printing time is longer than other 3D printing method

Applications

  • Medical devices

  • Implants

Polyethylene glycol (PEG)


3d bio-printed ear

3D bio-printing ear. Credit: 3Dnatives


PEG is one of the most widely used hydrogels in cell research, tissue engineering scaffolds and drug delivery system. It also plays a vital role in cell-filled 3D bio-printing. PEG-based hydrogels mimic the physical and biochemical characteristics of natural extracellular matrix (ECM) and demonstrate good biocompatibility under both in vitro and in vivo conditions. PEG materials allow hydrogel to be photo-crosslinked, which provides better mechanical stability after bioprinting.


3DP Technology: Bioprinting

Price: USD 200 – 300/kg


Pros