Page 82 - Flexible Robotics in Medicine

66 Chapter 3

provides up to 70-degree field of vision, and it is relatively lower when compared to the
Karl Storz 11101 VP/VN (85 degrees) and Olympus ENF-V3 (90 degrees).

3.5.8 Comparative advantages

3.5.9 Failure mode analysis

Failure mode analysis was done to assess the different situations in which the prototype
may fail. By doing so, we identified the components of the prototypes that are in the high-
risk failure mode and provide mitigation methods to ensure the safety of the prototype
(Table 3.14).
From the failure mode analysis, none of the risks are classified above 8. Hence the
prototype is relatively safe for subject use.

3.5.10 Other potential design conceptualization variations

Telescoping prototype (Fig. 3.11) was designed with three concentric tubes of varying
lengths, with the inner tube being the longest, followed by the middle and the outermost
tube accordingly. All three tubes contained the trench design to allow the cables to pass
along the walls of the tubing. The innermost and outermost tubes contained additional
diamond-shaped cuts to increase the flexibility and bending of the segment tip. The
outer tube would be inserted into the subject’s nasal inlet first, followed by the
middle tube and the inner tube accordingly. This prototype was fabricated using
the Stratasys Objet260 Connex 3D printer with 5% TangoBlack and 95%
VeroClear-RGD810.

The use of concentric tubes aimed to allow the subject to position and maneuver the
outermost tube first before inserting the middle tube. This allowed the subject to position
the outermost tube such that it is in minimum contact with the surrounding tissues before
guiding the second tube deeper and nearer to the nasopharynx region. The aim was to
increase the comfort of the subject. However, due to material and anatomical restrictions,
the fabrication of this design at small scales resulted in poor mechanical properties of the
prototype. Furthermore, friction between the tubes resulted in difficulty in inserting the
second and third tubes. Additionally, this design made use of 12 cables to operate,
which may be too difficult and tedious for the usage of the subjects. Even with two
concentric tubes, the mechanical strength of this prototype was still not rigid and
robust enough, and the bending capability of the tubes at the trenched portions
was too low.