Medical Design Briefs - July 2022 - 16

Engineered Extrusion Trends
momentum. An emphasis on preventing
the spread of infection from one patient
to another also is increasing.
Continuous innovation in drugdelivery
systems is expanding demand
for customizable tubes. In addition, innovations,
such as intra cochlear drug
delivery and photothermally triggered
drug delivery, are expected to lead to
growth in nano medical tubes.
Less-invasive medical procedures offer
the advantages of lower cost, as
well as quicker recovery times and
shorter hospital stays for patients.
These procedures are therefore increasing
in importance compared to
conventional surgical procedures,
which in turn is increasing the market
for tubing used to make such procedures
possible.
The trend toward less-invasive procedures
also places technical demands
on the devices to be designed in increasingly
smaller and complex ways.
Medical tubing applications. In
terms of applications, the medical
tubing market is categorized into
bulk disposable tubing, drug-delivery
systems, catheters, biopharmaceutical
laboratory equipment, and other
categories.
Stent tubes and implant-grade
tubes are anticipated to boost market
growth. Advancements in wound
therapy, in which tubes are used to
remove infectious materials and fluids,
also is expected to drive growth
in the sector.
Market by material. The medical tubing
market is categorized in terms of
Application Examples
Bioprocessing Flow Tubing
Application: Tubing to give a high-flow-rate discharge through a
large-volume bottom outlet disposable biobag.
Issues:
* Desired flow rates were not being achieved.
* Tubing was collapsing due to large suction pressure.
Solution: Tubing wall was increased to 0.48 mm/0.188 in. from 0.32
mm/0.125 in., while maintaining the same inner diameter. The thicker
wall prevented the tubing from collapsing, and the specified flow rates
were met.
Central Vascular Access Catheters
Application: Multilumen tubing and liquid-injection overmolding
connectors for central vascular access catheters.
Issues:
* Maintaining orientation of feeding lines.
Solution: Multilumen tubing and overmolded connectors utilized a
combination of high-precision, liquid-injection molding and extrusion
production techniques.
Orthopedic Tubing
Application: Extrusion used in an orthopedic additive-eluting medical
device.
Issues:
* Outer diameter less than 0.012 in. required.
* Precisely control a specific elution curve of consistent concentration
over a lengthened release time.
Solution: Close collaboration that started with the elution concept.
Using a single material resulted in a narrow two-layer extrusion with
the core serving as an eluting rod and an outer concentric layer that
precisely regulates elution in MIS procedures. The entire cross section
was under 0.012 in. Customer measurement fixtures were developed
and validated with the process.
Implantable Neurostimulator
Application: Electrical pulses to the brain and spinal cord are used for
chronic pain therapy and to treat disorders such as epilepsy, Parkinson's,
and Tourette syndrome.
Issue:
* Leads must be very small while maintaining insulation properties to
deliver the neurostimulating signals to precise locations.
Solution: Extremely tight tolerances were met with a microextrusion
made possible with advancements in quality process control and monitoring
systems. Diameters of ≤0.030 in. and required tolerances of 0.001
in. inner diameter, outer diameter, wall thickness, and concentricity to
allow for assembly of the conductor ensure sufficient and consistent
insulation along the length of the lead and minimize the overall size.
Pacemaker Lead
Application: Insulating, biocompatible extrusion carrying multiple
conductors for a pacemaker lead.
Issues:
* A strain relief method was needed to mitigate risk of breaking due to
dynamic loading.
* The multilumen extrusion design included more that 30 dimensions
with tolerances of 0.002 in. or less.
Solution: Employed continuously twisted tubing process technology with
custom tooling and measurement fixtures to validate the process
capability of all required dimensions.
Heart Pump
Application: Cable jacketing.
Issue:
* Provide a biocompatible, protective layer to a cable assembly including
several conductors, insulators, and strength members.
Solution: Developed and validated custom extrusion tooling in conjunction
with a precise cure parameter window to apply a silicone jacket around the
outside of the cable assembly without damage to internal cable components.
16
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Medical Design Briefs, July 2022
materials into polyolefins,
silicone,
polyvinyl chloride (PVC), fluoropolymers,
poly carbonates, and others. PVC
is the most widely used thermoplastic
material in medical tube manufacturing,
but silicone is seeing significant
growth.
The demand for PVC tubing is
anticipated to increase owing to the
rising demand for single-use presterilized
medical devices, which are
transparent, biocompatible, and offer
high resistance to chemicals. PVC
led the market and accounted for
29.5 percent of the global revenue
share for tubing in 2020 while silicone,
with its inherent suitability, in
particular for implantable devices,
is estimated to be the second-fastest
growing segment.
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Medical Design Briefs - July 2022

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