customized molecular weights that will facilitate more controlled
degradation of printed devices is an area of relative immaturity and
significant potential research.
High-temperature polymers are printed using high-end extrusion
technologies and powder bed fusion technologies, known by the
branded name Selective Laser Sintering (SLS). SLS’s unique
combination of heated build chambers and focused laser beams
allow for materials with higher melting points.
The most common printed material in powder bed systems
is nylon. While Nylon 11 has been commercialized to some
extent, Nylon 12 is the most popular laser sintered material, and
it is sometimes used to create surgical guides. With respect to
implants, Polyetherketoneketone (PEKK) parts are most common,
although they are utilized for lower-impact implant applications
like spinal and maxillofacial. For higher impact applications like hip
and knee applications, metals are more frequently used for their
superior impact and cycle time properties with respect to stress.
Not every high-temperature plastic is printed with ease.
Nylon 6 and Nylon 6, 6 are under development and used mostly
in academic settings. Polyether ether ketone (PEEK), another
material being tested in a variety of academic settings, is also
on the horizon. The challenge of maintaining tight temperature
windows across the totality of a build for existing machines has
limited PEEK’s commerciality to date.
Resins are also used in the medical field, but the applications are
primarily for instrumentation and surgical guides. Material-jetting
technologies, which behave much like traditional inkjet printers,
can deposit multiple materials within a single print. This can be
especially useful for applications like authentic reproductions
of internal organs. In such situations, digital imaging and
communications in medicine (DICOM) data can be converted to
printable files. These can be printed in multiple materials and colors
to offer surgeons a practice run before operating on a live patient.
Surgeons report increased efficiency in the operating room as
a result of these practice models. Peter Denmark, sales head for
Envisiontec, says surgeons report several minutes of savings from
the use of surgical guides before entering the OR.
“When you consider that an hour in the OR may cost $15,000,
saving just a few minutes can drive some very meaningful
efficiency savings.” Denmark says.
Bills are being reviewed in Congress that may facilitate increased
insurance coverage for such prints, which would accelerate adoption
of the technology in hospital environments, according to Denmark.
The frontier seems to be multi-material printing in the
thermosets world. Stratasys unveiled its multi-material Connex
J750 earlier this year, capable of printing with up to 6 materials
and more than 360,000 colors to allow for complex anatomical
models. Its competition has not yet followed suit with machines
providing similar levels of multi-material printing, although this is
something to watch.
Metal material suppliers started developing their products with
an eye to the aerospace industry, but in recent years have been
expanding their offerings to meet the demands of the medical market.
Powder bed printing is the default printing process for
metal medical parts. Using either a laser (e.g., DMLS, SLM,
LaserCUSING) or an Electron Beam (EBM) system, powdered
metal is selectively melted, layer-by-layer, to build a part. Printed
metal implants are growing in popularity, due in part to the ability
to build parts to fit particular anatomies. IN addition, the natural
surface roughness of powder bed printing has been found to
accelerate osteointegration. The biggest announcements in this
area have come from Europe and Australia, although significant
movement has been taking place in the US with the FDA’s recent
draft guidance to device manufacturers.
A variety of stainless steels with strong anticorrosive properties
are available, most notably 316 and 17-4, which are typically
processed using laser systems. Titanium alloys, which are printed
by both laser and electron beam systems, are also prevalent in
the medical space, with applications across instrumentation and
implants. Ti6AlV4 and Ti6AlV4 ELI are two alloys that are popular
for things like spinal implants, acetabular hip cups, and knee joints.
Recent announcements include commercially pure titanium,
which some doctors believe provides faster integration with bone
structures, although clinical data is still being gathered to see if
that hypothesis is correct. Cobalt chrome is another material that
sees use, although not with the frequency of titanium.
With respect to the future, 3D printer OEMs are generally mum
on which materials are on the way, although they are active in
encouraging the market to highlight which materials they’d like
to see commercialized next. It’s also expected that the growing
number of metal machines which provide more open architectures
will allow for the development and printing of bespoke alloys for
About the author: Cullen Hilkene co-founded 3Diligent,
the B2B Marketplace for industrial-grade 3D printing and rapid
manufacturing and serves as the company’s chief executive
officer. He can be reached at email@example.com.
Figure 2. Printed anatomical
bodies, like this full-size and
miniature liver with cancerous
bodies (blue), allow surgeons
to analyze and practice
surgeries before entering the
OR. Photo Credit: 3Diligent
Figure 3. Printed parts designed to interface with a rib cage. Photo Credit: CSIRO