(Updated on 14th May 2023)
Choosing the right materials and the printing technologies are among 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.
Credit: Tom Claes on Unsplash
Table of Contents
How medical 3D printing works?
Over the past decade, 3D printing is getting increasingly significant 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 or a STL file. In clinical settings, 3D printing has been well utilized to create physical anatomical models of body parts or organs of an individual. The physical 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 with better efficacy for producing tailor-made implants (PSI, patient specific implant), 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)
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, or even PMMA and PEEK which are more popular in implants) through a heated nozzle, and then applying layer-by-layer until the object is completed. While FDM is user-friendly and relatively cheaper in establishment, FDM is not suitable for printing metallic materials. In the case where very high strength has to be achieved like joint-replacement implants in load-bearing region, metal 3D printing achieved by Selective Laser Sintering (SLS) followed by machining will be a better option.
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 friendliness and ease to produce high quality, high-accuracy, isotropic, and watertight prototypes and parts. In addition to basic choices of resins (the printing materials), a wide range of advanced materials composited with ceramics and other other material fillers can be chosen.
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 higher resolution and accuracy, the clearer details, and the smoother surface among the plastic 3D printing technologies. Depending on the light sources and projection mechanism, DLP (Digital Light Processing) is a similar technology compared to SLA. In SLA, the UV laser has round edge and smooth lines can be drawn. In DLP, an imaged comprised of many rectangular pixels is projected layer-by-layer, so the smooth lines are made up of of rectangular pixels instead of round pointer like drawing with a pen in SLA.
SLA resin formulations cover a wide range of properties, but not as many as in FDM thermoplastics. The limitations of formulating a photosensitive liquid resins for use in SLA/DLP have restricted the choices of materials that can be applied. In general, the finished products printed by SLA are more fragile compared to FDM and SLS technology. However, the printing quality of SLA is less susceptible to increment in printing speed as compared with 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 powders or even metal powders, fusing them to build a solid structure. The polymeric materials used in SLS are thermoplastic polymers that come in powder 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. However, the surface of SLS printed parts are not smooth and serious polishing would be necessary. 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 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.
Material Selection Criteria
There are 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
Selecting a material by functionality
Followings are more detailed material properties you may consider when choosing the right 3D printing materials:
Source: Formlab, IJSRP, Conserve Energy Future, ScienceDirect, Wiki, ResearchGate, Fabbaloo, Reading Plastic
Typical 3D Printing Materials in Medical Field
Polylactic acid (PLA)
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)
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
Polyetheretherketone (PEEK)
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.
Medical grade PEEK is available in filament form for all FDM/FFF machines, and is slowly becoming available in high quality powder form for medical device production with 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 (Industrial Grade FDM Filament): USD 300 – 750/kg
Price (Medical Grade FDM Filament): USD 1,000 – 3,000/kg
NOVUS offers medical grade PEEK filament at less than USD 800/kg readily available online.
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)
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)
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 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 an 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 has developed a Medical Grade PMMA Filament and Bonelcule, a PMMA-based Bioactive Filament with the addition of nano-hydroxyapatite coated copolymer, which offers bone-like properties and accelerates implant-to-bone integration as an alternative to non-bioactive PEEK. Both medical grade PMMA filament and Bonlecule are readily available in NOVUS's online store.
3DP Technology: FDM / SLA / SLS
Price (Medical Grade FDM Filament): USD 200 – 1000/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
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: Varies largely based on the quality and printing technologies
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
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 500 – 1000/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-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: Varies largely based on the choice of materials and printing technologies
Pros
Good mechanical stability
Biocompatible
Cons
Synthetic material
Does not provide biological cues for cell proliferation
Relatively difficult to print
Applications
Vascular tissue
Bone tissue
Cartilage tissue
Typical Regulatory Requirements for 3D Printing Materials
In general, materials used in implant production should follow the requirements list in international standard related to biocompatibility, namely ISO 10993 and USP Class VI. USP Class VI refers to a set of biocompatibility testing requirements from the U.S. Pharmacopeia (USP). In 3D printing, materials should also follow similar based requirements in ISO 10993 and USP Class VI. However, additional requirements should be satisfied for patient specific implants registration, which include implant design SOP and 3D printing procedures.
There are already a number of biomaterials which satisfy ISO 10993. A summary of commercial non-metallic materials for additive manufacturing fabrication is reported.
Monzón, M.D., Paz, R. and Bordón, P. (2023) ‘Present and future of standardization of additive manufacturing in the medical field’, 3D Printing in Medicine, pp. 361–378. doi:10.1016/b978-0-323-89831-7.00007-9.
In NOVUS, we offer a variety of novel materials for 3D printing! We are working with OSSFILA to offer Bonlecule, a PMMA based bioactive FDM filament with hydroxyapatites, a medical grade PMMA filaments and even medical grade PEEK to unleash your creativity in producing all kinds of implants.
Please check out our catalog to learn more about the details!