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Flexible drill manipulator utilizing different rolling sliding joints for transoral drilling 437
Table 19.3: Comparison between Goldrill versions with different cross sections.

as a substitution. Therefore, the dimension of the handle is catered to that of the ratchet gear,
and the gratings present are to fit precisely with those on the wrench handle.

These prototype versions allow us to test the effects of various segment locking designs as
well as the placement of the tendon wires. Arranging the wires in a top bottom format
should, in theory, generate a better moment arm when pulled compared to a left right
format. This is because most of the force is exerted from the top by the drill tip in a
downwards Z direction to the segment. Thus, a top bottom format should allow a more
stable bending segment to be formed. Then Goldrill versions were compared in a series of
verification tests to determine the best design (Table 19.3).

Our final Goldrill GR3 is designed to be a separate system, which allows users to freely
change the Goldrill tube on the Goldrill handle based on the customized needs. Therefore,
the one-body handle design is changed to a square catch. Instead of VeroClear (the
material used in prototype), we intend to use steel for Goldrill tube, which gives much
more strength against breakage. We can further reduce the cross-sectional diameter.
Moreover, we can remove the need for a PTFE tube to protect our device against drilling
wear. We can instead apply biocompatible lubricants in the drilling hole to reduce the
frictional effects.

The Goldrill handle is introduced to replace the ratchet wrench in a prototype. The
ratcheting is provided by the inner brass component, which can be released from the gear
by pushing the pole, to allow free uncoil of the gear and thus release the wire to provide
flexibility. The four wires are connected onto a “cable tie” like a hard-plastic belt, which