Page 393 - Flexible Robotics in Medicine

386 Chapter 16

Failure Cause of failure Harm Initial risk Risk controls and
mode Likelihood Severity mitigation measures
Pin that Due to the sheer Ring is left in 2 2 Benchmarking from
supports force experienced the nasal cavity existing tilting
the ring while pulling the cameras. Minimize
breaks wires shear on the pin in
design
Wires used Due to the tensile Wires may cut 2 2 Benchmarking from
for the pan force generated by the subject if it existing devices.
and tilt the motors during breaks in the Reduce tensile
motion maneuvering of the nasal cavity strength on the wires
breaks camera
Sheath Repeated bending Might contact 2 2 Limit shelf life of the
tends to moment applied to the nasal cavity sheath
bend the tube causing of the subject
sheath deformation and cause
damage

The biocompatibility of the material is the quality of not having a toxic or immune reaction
to the biological system. The material considered for our device is benchmarked to those
already commercialized and proven safe for usage as an endoscope. It is also essential that
standards from ISO and American Society for Testing and Materials (ASTM) are followed
and adhered to. The following ASTM standards are used for the evaluation of the material
used for an endoscope, biocompatibility test methods, and electrical insulation of wires:

There are two materials used in making the prototype of P.A.T.S. The first material is
VeroClear, which is a rigid, hard, and colorless material used to make the camera holder
and the tip of the device. The second material used to make the sheath is TangoBlack,
which is a rubber-like material that has excellent mechanical properties such as hardness,
tear resistance, and tensile strength. The insertion of the device through the nose plate
(accessory) is curved. Thus TangoBlack is chosen as the material for the sheath because the
sheath has to be slightly bendable to pass through the curved part while maintaining its
excellent mechanical properties to prevent it from deforming. However, VeroClear is to be
replaced by medical grade stainless steel (316L) in the future because VeroClear is still
considered not mechanically strong and stable as compared to stainless steel. On the other
hand, TangoBlack is also replaced by nitinol, which has stronger mechanical properties
while being able to bend to pass through the nose plate and being able to recover when
removed.

16.7 Conclusion and future developments

The function of the device is to enter nasopharynx to monitor whether there is a
growing tumor (NPC) in the region. The camera can tilt left or right, covering the