The Form 1+ gave the team a chance to relax more during the
design process. “If you are waiting five to 10 days for parts from
a bureau, you often find that you have moved the design in that
period to such a degree that the parts arrive and are no longer
valid,” says Berry. “Or you try and over design the part with
various options, which takes more time.”
According to Will Walker, Formlabs’ senior marketing
designer, both Sutrue and the medical prototyping industry are
using low-cost prototyping to test more products, faster. “It’s an
exciting time to watch the industry, because the barrier to trying
new ideas is lower than ever before,” he explains.
Solving a Complex Design Challenge
Although the Form 1+ expedited the prototyping process,
Berry and his colleagues did run into a few design challenges.
Engineering 101 says that gears should be at a set distance
apart. The smooth running of gears relies on this precise
distance and mechanical designs must take this into account.
“It took several years and a few prototypes to realize that
although that tenet is true, with slow running gears you can
change that separation distance ever so slightly,” says Berry.
So, he designed a system where the gears used to drive
the rollers, which themselves drive the needle, sit on a sphere
and are controlled by a perpendicular spring plate. This allows
fractional rotation on the z-axis and tension between the rollers
and needle that drive it through the tissue.
In order to verify that Berry’s design was viable, he enlisted the
help of a surgeon from the Royal Brompton Hospital in London,
Dr. Richard Trimlett. Dr. Trimlett has been helping the design
team for nearly six years, not only on the user perspective, but
also on the engineering side as well.
“[Dr. Trimlett] has been instrumental in understanding what the
end user would require for the best application of the device and
has performed all our trials and tests,” says Berry.
All of the device’s testing has been performed on a custom rig
to verify the amount of power the team can generate behind the
needle tip. Dr. Trimlett then performs the trials with a series of
tissues, such as a heart or artery.
The tissue trials allow engineers to examine whether the
Sutrue device does indeed provide advantages over suturing by
hand. Aside from the prevention of needle-stick injuries, Berry
and his team believe the device will speed up suturing, because
the needle can be driven in a full circle at speeds up to once per
second, and there is a backwards option in case of mistakes or
In addition, the device provides a constant angle of rotation
with no variation, essentially eliminating the variation in
placement attained by manual stitching.
Further Testing & Trials
Berry believes that the simplicity of the Sutrue device will
permit a greater number of clinical staff to be trained in suturing,
allowing it to be practiced in a broader range of clinical settings
– not just in hospitals and emergency situations.
The team also wants to take the automated suturing technique
into the realm of endoscopic keyhole surgery. In fact, Sutrue just
finished prototyping the endoscopic version of the device, which
the company plans to test as early as February.
“For endoscopic or robotic suturing, although there are
currently devices that can suture, they all have bespoke needles
and don’t emulate how a surgeon normally turns a needle during
manual suturing,” says Berry. “We foresee our device being
available for more procedures using more than one type of
needle if necessary.”
While both the external and endoscopic Sutrue devices
benefited greatly from 3D printing in the prototyping phase, it’s
time to move on to the materials phase of development. Berry
and his team must find materials that are biocompatible and
suitable for human trials.
However, he recognizes that the Sutrue devices would likely
never be possible without the use of 3D printing.
“There is so much that can be designed and modeled using
3D printing in both plastics and metals,” muses Berry. “If it’s
possible in the physical world, then it’s possible to print.”
The Sutrue device uses
several sets of tension
rollers to drive the needle.
Alex Berry and his team just finished
prototyping an endoscopic version
of the Sutrue device.
The Sutrue device was prototyped with
the help of the Form 1+ SLA 3D printer.