ILMA Compoundings August 2018 - 20

Lubricants play a role in nearly every
part of the medical equipment realm
in one form or another.

turers require having safe products, but that is not all - the
metalworking products also need to be easy to clean in order
to obtain 'extremely low residue' status. It's a plus that any
residue left on the devices is considered safe, but it's best to
have virtually no residue."
Lubricant use isn't restricted to large pieces of equipment
or machinery, though - smaller devices such as syringes (as
well as other instruments with gaskets and seals), medical
tubes and catheters also require high-quality lubricants or
polymers to function properly.
"Of interest from a tribological point of view is the way
that fluids wet a surface and how one can affect the force

needed during cutting or injection of needles," said George
Fenske, program leader in Argonne National Laboratory's tribology department. "Drills and burrs used to remove plaque
from vessels (atherectomy) are engineered to selectively cut
plaque while minimizing damage to surrounding vessels."
Even something as simple as contact lenses for vision
correction involve tribological forces, since "the design of lens
material with appropriate optical and tribological properties
ensures proper lubrication of the lens," he said.
Body implants illustrate another key area in which
lubrication is essential to the success of the medical implant
- in this case the lubricant is viscous non-Newtonian
fluid naturally ocurring in synovial joints. Artificial hip and
knee replacements make use of articulation that require
lubrication of a high quality, as these parts are under almost
constant physical manipulation and stress. Lubricants are
also needed in artificial spinal discs, bone plates and screws,
and degradable implants. There is even an entire field of
study dedicated to the science of friction and wear within
the body and how lubricants can be used safely for human
patients with artificial implants - biotribology. Fenske
explains that "injured or damaged joints are replaced with
materials (polymers, ceramics and metallic alloys) engineered
for biocompatibility, strength and durability. The tribological
performance is critical, as small amounts of wear debris
that form when the artificial components slide against one
another may cause an inflammatory reaction with bone
absorption, which can cause loosening. This phenomenon is
known as osteolysis."
Lubrication and health care are linked in perhaps an even
more foundational way: Blood flowing through veins and
arteries is, in fact, tribological in nature.
"For issues related to the flow of lubricants in engines, we
are concerned about deposit formation and agglomeration
on critical surfaces," explained Fenske. "One could use the
same comparison to the flow of blood, wherein triglycerides
form deposits (plaque) that reduce the flow of blood. In both
cases, additives are introduced to mitigate the formation
of deposits."
"Another example where tribology comes into play in
blood flow is an artificial heart, or ventricular assist devices,"
he continued. "The designs are still evolving, and careful
consideration of hydraulic flow of blood through the pumps
is taken to provide sufficient flow and pressure while minimizing mechanical shearing of blood."

Medical Fabrics and Pharmaceutical Applications
Medical apparel, including gloves, face masks and surgical
gowns, needs to provide an impenetrable barrier between the
wearer and sources of contamination. Fabrics and apparels
Continued on page 23

20

AUGUST 2018

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ILMA Compoundings August 2018

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