Page 64 - Flexible Robotics in Medicine

48 Chapter 3

minimize the discomfort of the subject as it eliminates the need to insert the endoscope
deeper into the nasopharynx manually; thus contact with the deeper tissue structures can be
minimized.

The diamond-cut design on the FlexDiamond increases its flexibility and allows it to
achieve a sizeable bending angle in order to monitor the entire region of the nasopharynx
effectively. Due to the limitations of the prototyping material used, the bending angle that
the endoscope can achieve can be further optimized in the future.

3.3.2 Overall design

Fig. 3.1 shows the functional prototype, with a total of 3 DOF. The prototype consists of
the following components: cap for camera head mechanical zooming segment, bottom cap
for zooming segment (with one threading hole), cap for bending segment (with four
threading holes), bending segment (four holes along the wall thickness of the tube), bottom
cap for bending segment (with four threading holes), and five cable control system for
insertion of the endoscope (housing for gear mechanism).

3.3.3 Design components and design rationale

3.3.3.1 Mechanical zooming segment
The camera is attached at the tip of the endoscope and further secured using the camera
cap to prevent the camera from detaching during endoscopy. The front segment of the
endoscope functions with the capability of extending and retracting the camera in the axial
direction (z-axis). This mechanism works via the use of spring compression or extension.
When the endoscope is first inserted into the nasal inlet of the subject, the front segment
will be in a compressed state. After the endoscope reaches the nasopharynx region, the
subject is able to extend the spring to allow the mechanical zooming of the camera in
order to capture a clearer image of the nasopharynx region. The camera can zoom up to
5 mm by using a single cable that is passed through the core of the endoscope.

3.3.3.2 Bending segment
The back portion of the endoscope is the bending segment responsible for the viewing angle of
the camera. With 2 DOF in this segment and a bending angle of 90 degrees in each direction, it
enables the camera to view a large area of the nasopharynx of the subject. For this segment,
2
ESC-CY4-25, with a spring constant of 0.03kg/s , was fitted in the lumen. The bending segment
is actuated using four cables, and each cable is responsible for bending in one direction. This
allows the endoscope to bend in the x- and y-axes (Fig. 3.2). Due to the flexibility of the
prototype, appropriate control of the cables will also enable us to bend the endoscope diagonally