Page 488 - Flexible Robotics in Medicine

482 Chapter 21

module consisting of the driving disc and cap (socket) was fabricated by medical grade
plastic, when the ball is made of rubbery materials. The base and case of the proximal
module are made from medical grade plastic or aluminum to reinforce robustness. The
insertion module we envision to coat with medical grade silicone or Polytetrafluoroethylene
(PTFE). Springs that are used to reinforce cable-driven control architecture better including
biopsy forceps are made of stainless steel.

21.3 Key features

OmniFlex promotes ease of usage with one-hand intuitive ball and socket control
and omnidirectional curvature. Shape-lock ability, on the other hand, enables multitasking
capability. No twisting of the prototype is required to touch hard to reach the targeted
spot. The curvature angle can be about 150 degrees in all four directions. Also, OmniFlex
is controlled mechanically, and no electronics parts required, which is why it is
lightweight, easy to handle, reprocess, and portable. In the proximal control module, ball
surface roughness induces shape-locking by friction. The driving disc is designed to be
easily manipulated by one hand with an appropriate diameter that also promotes actuation.
The case housing the cables is a temporary design that can easily be changed to become
compatible with different endoscopic manipulators.

Going from right to left, starting with the cap, is a cap, disc, and shaft, as illustrated in
Fig. 21.3. OmniFlex’s proximal end actuation mechanism is modeled after a ball and socket
joint. In this case, the “socket” would be a spherically shaped cavity formed when the cap
is twisted and locked onto the disc. Both the cap and the disc should be made of medical
grade plastic. OmniFlex’s disc has four loops spread out evenly to attach each of the four
driving cables. We spread them out as far as possible to amplify the curvature of the distal
flexible compression spring due to the tilting of our disc. OmniFlex’s shaft has a t-shaped
connecter to attach to the ball and four holes at the other end to allow the four driving
cables to pass it through. Medical grade plastic would be used for the shaft too.

OmniFlex’s distal part design is optimized to pull the manipulating wire to create moments
about the center pivot to close the jaws while pushing it will open the jaws. In order to
prevent the manipulating wire from buckling while transmitting push force, we braided the
manipulating wire with small beads. In order to connect OmniFlex’s distal flexible
compression spring to flexible cable housing (60 cm long extension spring), we needed a
spacer, which was also useful in guiding our four driving metal cables. From Section A-A
in the drawing below, our spacer was designed to allow the four driving cables to run
through the interior of our flexible cable housing but run alongside the exterior of our distal
flexible compression spring. The reason why we had the four cables running outside our
flexible compression spring was to allow for a larger moment arm and better actuation.