Medical Design Briefs - December 2021 - 12

High-Value Products
Typically, this relates to raw
plastic material applications
with incompatibility issues
that exist.
Plasma can transform the
surface properties of plastic
to achieve aims that normally
would not be feasible
[without treatment]. This
can include cleaning surfaces,
resolving difficulties
applying printing inks to
plastics, improving the ad -
hesion of plastics to dissimilar
materials, and applying
protective coatings that
repel or attract fluids.
Plasma today is
being
used to treat various medical
device products, such
as syringes. Manufacturers
of plastic parts are always
looking for unique ways to
gain a technology edge to
become a market leader. To
achieve this today, top tier
products incorporate some
form of advanced coating
to functionalize the surface.
When the medical
device industry uses plastics,
more specialized offerings
can create a competitive
advantage and drive up
the value of each part or
product. When plastic is
treated with plasma, it can
transform a two-dollar item
into a fifty-dollar product.
This article outlines some
of the essential areas of plasma
treatment in the medical
device industry, including
printing on plastics, micro -
fluidic devices, bonding
plastic with dissimilar materials,
Printing
on Plastics
When printing on plastics is required,
binding the ink to the surface can sometimes
be challenging; this occurs when
the print beads up on the surface or
does not sufficiently adhere to the surface.
Greater print durability may be
needed, including fade resistance, even
under high heat or repeated washings.
For example, to resolve the beading
issue, plasma treatment can make the
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This wettability promotes
superior adhesion using
chemical adhesives.
On the other hand, substrates
with low surface
energy - such as silicone
or PTFE - are difficult to
adhere to other materials
without first altering the
surface to increase the free
energy.
Depending on what is
required, organic silicones
can also be used to create
intermediate bonding surfaces
with either polar or
dispersive surface energy to
help printing inks adhere
to the surface of the plastic.
This approach can facilitate
the durable printing of a
logo on the surface of bottles
when the logo cannot
fade after
the first wash.
Another application includes
the printing on plastics
used for syringes, which
do not bond easily with
biodegradable inks that are
friendly to the human body.
Microfluidic Devices
Typically, microfluidic systems
used for medical or
industrial applications trans -
port, mix, separate, or otherwise
process small amounts
of fluids using channels
made of plastics, measuring
from tens to hundreds of
microns.
Extremely consistent and uniform nitriding batch-to-batch, with less gas consumption
are achieved with a new chamber design. (Credit: PVA TePla)
treating plastic labware coating
plastics to prevent leaching, and facilitating
R&D.
surface hydrophilic (attracted to water).
The treatment facilitates spreading out
the ink on the surface, so it does not
bead up.
For many applications, plasma treatments
are utilized to increase the surface
energy of the material. Surface energy
is defined as the sum of all intermolecular
forces on a material, the degree of
attraction or repulsion force a material
surface exerts on another material.
When a substrate has high surface
energy, it tends to attract. For this reason,
adhesives and other liquids often
spread more easily across the surface.
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Microfluidic devices usually
have various wells containing
different chemistries,
either mixed or kept separate.
So, it is imperative to
either maintain flow through the channel
or prevent any residual liquid flow in the
channel after the chemistry has passed
through it.
With microfluidics, plasma treatment
is used to disperse liquid on the surface
to allow it to flow through easily. Or it
can make the surface more hydrophobic
(water repellent) to prevent the fluids
from clumping together in unintended
areas. When the fluids are pushed away,
this minimizes the chance of any sticking
or getting left behind.
In such cases, the plasma treatment of
these plastic surfaces can facilitate the
Medical Design Briefs, December 2021
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Medical Design Briefs - December 2021

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