Medical Design Briefs - September 2021 - 10

Ultrashort Pulse Lasers
unsatisfactory color or contrast changes in
imprinted labels. The processing window is
quite narrow when creating passivationresistant
black marks on stainless-steel components.
Marking with picosecond and
femtosecond laser systems have a much
wider operating window. This is because
the USP laser acts to modify the surface of
the material at the nanoscale, creating an
effect that essentially traps light, causing
the exposed area to appear perfectly black
even when viewed from all angles.
As a result, ultrashort pulse widths
and high repetition rates enable femtosecond
lasers and picosecond lasers to
excel in applications where nanosecond
lasers were traditionally utilized. They
depend less on the wavelength than
nanosecond lasers for marking materials,
and this aligns with increasingly
stringent FDA requirements to favor the
use of ultrashort-pulsed laser marking.
FDA Medical Device Mandates
Whether surgical tools, pacemakers,
reusable, nonimplantable devices, or
joint replacements, the medical device
industry will continue to rely on laser system
manufacturers for their expertise in
marking to ensure compliance.
Over the last few years, the FDA has
mandated that Class II devices and those
intended for repeat use or reprocessed
before each use, as per 21 CFR § 801.45,
must be marked with a unique device
identifier, or UDI. This is because these
latter devices inevitably become separated
from their original labels and device packaging.
This regulation applies to one-time
and multi-use stainless-steel instruments
and devices as well as when the term reprocessing
is referenced, which typically refers
to autoclaving (a sterilization method that
uses high-pressure steam).
There are a few ways that these
required laser markings can be inadvertently
removed during subsequent
cleaning processes. However, marks produced
using the picosecond laser or
femtosecond laser are far more robust
and survive the passivation process more
reliably than other laser types.
The FDA implemented such UDI regulations
to guarantee that hospital staff can
access the data encoded in these identifying
marks, and any failures at reading
these codes would generate records within
the FDA database. If the FDA finds that
there are numerous reports generated
for a given device or instrument, they can
initiate the shutdown of production while
they investigate.
Device Traceability
The markings help with tracking and
recordkeeping that device manufacturers
need to not only comply with government
mandates but also to address and
correct production errors, decrease
costs, and even at times defend against
any potential lawsuits. To maintain traceability
on tools and devices as they are
produced, distributed, or in use by the
patient, device makers can either permanently
mark via a unique number, barcode,
2D symbol, or logo on ceramics,
composites, metals, and/or polymers
that are used to make and package products.
This is done using a picosecond
laser to produce a clear, corrosionresistant
laser mark.
A picosecond and femtosecond laser
system delivers a unique laser mark that
survives multiple passivation, autoclaving
cycles, and repeated sterilization. These
devices, often made from various stainless
steels, need to be marked with highcontrast,
high-resolution black marks so
that operators or machines can easily
read them - all for the sake of traceability.
Achieving high contrast is key be -
cause after many cycles of autoclaving,
the high contrast can eventually pass
below threshold for certain automated
readers, which is problematic. It is critical
that these marks are fade-proof, and
the USP lasers do a very good job at this.
Understanding the Role of
Passivation
Picosecond laser systems are able to
produce marks on contoured surfaces.
The marking process, most importantly,
does not compromise natural passivation,
the process of treating or coating
stainless-steel surfaces in order to reduce
its the chemical reactivity of its surface.
The need for repassivation can be greatly
decreased or even eliminated, which
saves time and cost.
The laser processing procedure causes extremely dark, high-contrast markings on a surface without
material ablation. (Credit: ACSYS Lasertechnik)
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For generating black marking, the
laser processing procedure, which causes
extremely dark, high-contrast markings
on a surface without material ablation,
the picosecond laser system uses
ultrashort pulse durations that impart
energy to a steel surface with almost no
thermal effect. Unlike heat-generated
annealed marks produced from other
lasers, black marks created by a pico -
second laser system provide substantially
high contrast periodic nanostructures
with antireflective properties. This contrast
makes the marking appear deep
black against its background.
As opposed to an oxide layer, the
restructured surface is greatly resistant
to bacteria forming, passivation, corrosion,
and autoclaving. In addition, this
laser system offers a much wider processing
window for marking stainless steel,
aluminum, and titanium than standard
Medical Design Briefs, September 2021
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Medical Design Briefs - September 2021

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