Page 427 - Flexible Robotics in Medicine

Flexible drill manipulator utilizing different rolling sliding joints for transoral drilling 421

In recent years, there are many medical devices with an articulating such as laparoscopic
retractors and dissectors. The bending of the flexible section in these designs can be
actuated by various mechanisms. The more common actuation mechanism is cable-driven
systems with sliding joints applied over modular segments. For example, US Patent
6,248,062 B1 uses a uniform hinged sliding joint mechanism that allows the shaft to
accommodate the shape of the environment. By locking the adjustment mechanism on the
distal end, the proximal end of the shaft can curve into its locked position to retract organs.
As for US Patent 5,522,788, it functions by using uniform rolling sliding joints and the
locking mechanism maintains the force on the dissector element to maintain the desired
curvature. However, the purpose of these two designs is focused on flexibility, which is
only the bending aspect of our design, and the features included do not consider stability,
which is the other main requirement of our design.
Therefore, there is a need for a device that allows bending movements while maintaining
stability to ensure that the drilling is specific and precise. Since the flexible drill
manipulator acts as a surgical tool for surgeons, being lightweight and easy to use would be
preferable. Taking all these into account, we decided on using different rolling sliding joint
designs at different modular shaft sections, with cable-driven mechanism, controlled by a
ratchet at the proximal end. This ensures that we achieve the stability aspect of our design.

The cable-driven flexible drill manipulator takes two forms: rigid or flexible. Rigid will be
at the state where the modular segments are coupled together by joints to form a serpentine
structure. The modular segments initially have six degrees of freedom, with movement
available about three axes. When coupled together, these degrees of freedom are constricted
to allow for tension control and directed bending of the manipulator.
Flexible systems can be classified under serpentine, as mentioned above, or continuum.
Continuum nature takes on the form of a continuous singular element such as a flexible
tube. Bending ability, in this case, mostly relies on material properties such as stiffness and
thickness of the tubes used. One example would be US Patent 7,989,042 B2. In our case, a
continuum is not as ideal as the flexibility of the tube may cause instability. One can argue
that we can change the material stiffness to achieve stability. However, stability and
flexibility are both what we want to achieve. Hence, serpentine will be the ideal choice
since we are able to achieve both without compromising either criterion.

19.3 Goldrill device: flexible endotracheal drill

In contrast to the current outside-in methods, our device aims to reduce the damage to the
tissue by creating the opening from the inside of the trachea. Tracheostomies from inside,
also known as transoral tracheostomy, allows for greater accuracy of an incision, therefore
minimizing the risks involved in inexact surgeries.