29 / 78
also being used to deliver medicines directly to organs.
For example, a plastic spongelike material is doped
with medicine and inserted into the liver, dispensing
medicine at a consistent rate and lasting from six
months to three years before dissolving. Figure 4 shows
an fs laser cut of a bioabsorbable stent.
After years of clinical trials, several firms are await-
ing approval and already planning for the new innovation
to hit the U.S. market, and several have been qualifying use
of fs laser equipment to gear up for the precision micro-
machining required.
Femtosecond lasers
for micromachining
The industrial strength of the disk fs laser must be
matched to an equivalent system to deliver the consistency
and reliability required by the medical device industry.
Today’s fs lasers cannot be fiber-delivered and are there-
fore directed and delivered to the focusing optics by fixed
mirrors—a challenge for designing a beam delivery system
for a four-axis tube cutter that can make off-axes cuts while
maintaining alignment. The optical path design must en-
sure that the beam expander and fine-tuning attenuator
are easily accessible for process development. System de-
sign requires full mechanical isolation, and in some cases
ambient temperature stability, to provide a foundation for
process repeatability.
To gain the system integration capabilities needed
to move the femtosecond laser capability into the mar-
ketplace, a platform was developed based on Miyachi’s
Sigma Tube cutter (Fig. 5). First, the end user’s process
must be understood in order to determine a specific
application’s system needs. This level of understand-
ing can only come from running the application in-
house. Although this knowledge is important with any
process, it is magnified with ultrafast systems. An
in-house femtosecond processing lab provides transi-
tion from application development to the define-de-
sign-deliver approach for both standard and custom
system fulfillment.
While mechanical stiffness and isolation are re-
quired, they are only a starting point. Determining
how delicate parts and materials will be repeatedly po-
sitioned or clamped, implementing in-system part in-
spection and incorporating real-time optical beam
diagnostics are other key pieces. For example, mirrors
direct the beam through the system, so optical align-
ment is important, but this is only the first step. En-
suring that beam profiles and power levels are
maintained requires optical diagnostic tools—and
these tools must be in line and nonintrusive, providing
real-time information. The tool is usually mounted di-
rectly after the laser and the last turning mirror in the
beam path to enable deviations to be isolated to the
laser or the optical beam path. Being in line and non-
intrusive enables data collection during processing
that can be time and date stamped as part of the man-
ufacturing data.
Conclusions
The femtosecond disk offers unique process capabili-
ties with high beam quality and peak powers. To maximize
the process capability for production, the laser must be in-
tegrated into a system that enables high quality and repeat-
able processing.
For more information:
Steven Hypsh, Jenoptik, 16490 Inno-
vation Dr., Jupiter, FL 33478-6428, 561.881.7400 x 1197,
stephen@jenoptik.us,
jenoptik.com.
ADVANCED MATERIALS & PROCESSES •
NOVEMBER-DECEMBER 2014
29
Fig. 5 —
Femtosecond stent
and hypo tube cutter, covers
off, showing Jenoptik laser.