Page 67 - Flexible Robotics in Medicine

Cable-driven flexible endoscope utilizing diamond-shaped perforations: FlexDiamond 51

to be inserted into the nasopharynx region with a camera-illumination component for the
detection of NPC. FlexDiamond matches the identification of the nasopharyngoscope in
21CFR 874.4760. Therefore itself and its associated accessories are classified as Class II
prototypes with no exemptions in general and special controls.
A potential candidate as the predicate for FlexDiamond is the ENTity NasoView LED
Nasopharyngoscope (Model 006105, Optim LLC). Table 3.4 compares the intended use as
well as the technological similarities and differences between FlexDiamond and ENTity
NasoView LED Nasopharyngoscope.

3.4 Design verification

3.4.1 Mechanical strength tests

Mechanical strength tests were conducted to assess the mechanical strength of the materials
used to determine if the material is suitable for a particular application. Moreover,
mechanical tests allow us to determine the stability and durability of the prototype.

3.4.1.1 Tensile test for nylon thread (tendon)

• Aim: To determine the ultimate yield of the material to determine the maximum force
on the tension member (Fig. 3.3). (Experiment is developed from the scope from
ASTM D3822/D3822M-14.)
• Experimental procedure: Load the nylon string onto the Instron machine; conduct the
tensile test for the nylon string; apply load to the nylon string until the breakpoint.
• Results: The Young’s modulus and tensile stress of the nylon string are 916.48 and
280.73 MPa, respectively. The maximum load applied just before the breakage is
31.84 N.

Table 3.4: Comparison of FlexDiamond with ENTity NasoView LED Nasopharyngoscope.
ENTity NasoView LED
Prototype name Nasopharyngoscope FlexDiamond (nasopharyngoscope)
Prototype classification name Nasopharyngoscope Nasopharyngoscope (flexible or rigid)
(flexible or rigid)
Intended use Oral or nasal insertion A home-based examination of the nasal
by a clinician cavity via the nasal introduction
Material (rigid or flexible) Flexible Flexible (polyurethane)
(aluminum 1 sheath)
Technology Cable-driven Cable-driven
Insertion tube diameter (mm) 3.6 7
Articulation 135o(x- and y-axes) 90o(x- and y-axis) 1 5mm (z-axis)
% %
Working length (cm) 30 30