Page 255 - Flexible Robotics in Medicine

244 Chapter 10

The bending angles could also be improved by changing the location of the SMA wires in
the tentacle structure. The bending angle increases as the SMA wires are placed away from
the neutral axis. This encourages to place the SMA wires close to the periphery of the
tentacle structure. Achieving this arrangement will require the sophisticated fabrication of
the mold. Repeated exposure of thin silicone elastomer to high temperature could damage
the silicone and expose the SMA wire to the nasal cavity, which could damage the tissues
in the nasal cavity. A problem with using the SMA wire is the precision of temperature
control, which leads to the precision of the position of the tentacle structure in this
application. Adding a sensor system installed that is capable of dynamic feedback through a
close-looped system, in turn, can be used to control the overall heating rate. The bending
curvature could be further improved by reducing the length of the tentacle structure.
Another option would be to have a passive component made of a stiffer material and the
active component being shorter with the silicone elastomer. This will allow the active softer
component to navigate in narrow regions such as the eustachian tube, while the passive
stiffer component remains in the nasopharyngeal cavity. This could be widely used in other
minimally invasive surgeries where longer tentacles are challenging to navigate.

10.4.1 Comparison of the tentacle with the products in the market

Eight-millimeter robotic instrumentation is a reasonable size for use in transoral surgeries.
In Ref. [34], the primary robotic instruments used were the Endowrist 8-mm precise bipolar
cautery. In transoral surgeries such as the laryngoscopy, where procedures are done to
obtain a view of the vocal folds and glottis, the size of the current prototype satisfies the
requirements comfortably. The Glidescope, designed by a general surgeon, was one of the
first commercially available video laryngoscopes. Its successors are still widely used for
surgeries these days. The Glidescope Video laryngoscope incorporates a high-resolution
miniature video camera positioned on a curved laryngoscope blade angulated at 60 degrees.
Karl Storz DCI works in a similar fashion to provide a view to the vocal glottis. These tools
do not supply a bendable tip to increase viewing angle, and the innate camera used only has
a viewing angle of 50 degrees [35]. Fujifilm’s transnasal endoscope prototype, with a
diameter of 5.9 mm, has a viewing angle of up to 140 degrees and is capable of macro-
photography from a distance of just 3 mm.
Nasal endoscopies are executed with both the flexible fiber-optic endoscope and rigid
endoscope. Though the flexible type endoscopes can be extended into tighter cavities, it
requires two hands for manipulation. An endoscopic robot typically comes with a console
and works a patient-side cart with robotic arms. To provide perception within the operating
system, it has the in-site vision system, an advanced camera unit actuated by cables, and is
programmed to regulate the temperature of the endoscope tip to prevent fogging during
operation. Its endoscopes currently are 12 mm in diameter, housing two separate 5 mm