Medical Design Briefs - July 2022 - 20

Engineered Extrusion Trends
Barium stripes can be added to a tube
to make it visible within soft tissue, while
still enabling the fluid to be viewed to verify
flow. A higher percentage of barium
additive can be used to ensure that a tube
can be seen through bone, such as to
help a surgeon place a catheter in the
spine.
There is a limit to the amount of
radio paque additive that can be incorporated
and still render silicone processable
by extrusion, however. Even the
smallest additive amount can make silicone
visibly opaque without offering sufficient
radiopacity.
Tubing's Role in Enhancing Device
Design
Using this technology, numerous lumens or channels are produced as a single extrusion. More lumen
means more dimensions to control and measure. (Credit: Trelleborg Healthcare & Medical)
Platinum- cured silicones can be formulated
to bond with metals used in implants,
such as titanium, stainless steel,
and nitinol, and with plastics such as
polycarbonate, polyester, and PEEK.
Factors to Be Considered Before
Specifying Tubing and Hoses
Before designing tubing and hoses
for medical devices, engineers should
consider factors such as size, hardness,
tear strength, elongation, surface friction,
transparency, and visibility.
Size. Size is increasingly becoming a critical
factor in the design of tubing as medical
device developers seek to produce ever-smaller
devices and less-invasive drug-delivery
systems. Shrinking geometries and
tolerances can push the limits of process
control and create downstream challenges
with testing, measurement, and assembly.
Hardness. Extruded silicone is commonly
available in durometers from Shore
A 20 to Shore A 80. As the durometer increases,
tensile strength decreases, making
it an important factor to prevent break failures
in wound drains, for instance, which
are put under significant tensile load when
removed from the body.
Tear strength. Tear strength influences,
for example, how difficult it is for a
nick in a tube to propagate and is a consideration
in situations in which the tube
might be exposed to a sharp edge or for
geometry with small internal radii. Lower-durometer
silicones have significantly
lower tear strength.
20
Elongation. Elongation properties
relate to the elasticity of the tubing,
which is a significant factor for balloon
devices, for instance. Lowerdurometer
silicones have higher elongation
properties.
Surface friction. When it is important
for a tube to have minimal surface
friction, the tube can be coated to decrease
the material's inherent stickiness.
For instance, a coating can reduce
the forces required for deployment of
an implanted or interventional device,
like stents and balloons, or to facilitate
assembly of tight fits in devices like pacing
leads.
The coating or surface finish must
be biocompatible if it is likely to come
into contact with the body. Several
coatings are available that bond well
to silicone and meet compatibility requirements.
Transparency.
Visibility to verify flow
of media through a tube is important
for certain types of devices, such as
those carrying fluids into or out of the
body. Silicone, for instance, is naturally
translucent. However, certain silica fillers
that increase durometer, as well as
fillers such as barium sulfate (BaS04
and titanium dioxide (TiO2), can re)
duce
or eliminate transparency.
Visibility. Designers may wish to
make a tube more visible within the
body, to aid in guiding a device through
the body when viewing it using an x-ray
or fluoroscope, for example.
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Responding to rapid growth in the medical
device market, medical device manufacturers
are looking to innovative processes
to enhance their products and meet
patients' needs, including miniaturization
and wearability.
Hoses and tubing manufacturing
techniques are helping to support
these new developments and improve
patient quality of life with increased
function and enhanced integrity and
by enabling the incorporation of
APIs.
To facilitate manufacturing these
complex extrusions to client specifications
and with user experience in
mind, designers and manufacturers
should work with an expert in hoses
and tubing who can help identify and
prioritize critical features relevant to
the application and who can employ
progressive technologies and processes
to revolutionize medical device
design.
References
1. " Medical Devices Market 2021 - By Type Of Device, "
Global Forecast to 2023, The Business Research
Company, accessed Jun 1, 2022, http://
www.thebusinessresearchcompany.com/report/
medical-devices-market
2. " Medical Tubing Market Size, Share & Trends
Analysis Report, " 2020-2-28, Grand View Research,
accesses Jun 1, 2022, http://www.grandviewresearch.com/industry-analysis/medicaltubing-market
This
article was written by Dan Sanchez,
Product Manager, Trelleborg Healthcare &
Medical, Paso Robles, CA. For more information,
visit http://info.hotims.com/82323-340.
A detailed white paper can be downloaded at
https://www.trelleborg.com/en/healthcare/
tools-and-media/technical-library/
advanced-extrusion-whitepaper.
Medical Design Briefs, July 2022

http://www.thebusinessresearchcompany.com/report/medical-devices-market http://www.thebusinessresearchcompany.com/report/medical-devices-market http://www.grandviewresearch.com/industry-analysis/medical-tubing-market http://www.grandviewresearch.com/industry-analysis/medical-tubing-market http://info.hotims.com/82323-340 http://www.medicaldesignbriefs.com

Medical Design Briefs - July 2022

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