Page 444 - Flexible Robotics in Medicine

438 Chapter 19

entirely bites on gear. When the user turns the gear using the extruded “trigger,” the wire
will be tightened. Based on our estimation and measurement on a prototype, a 30 mm
allowance of wire (fully released compared with fully tightened) can provide enough
flexibility for the Goldrill tube to reach the drilling site. This length is translated into gear
circumference and subsequently to the maximal rotation angle of the gear (B70 degrees
with gear outer diameter 55 mm), and we design our opening for trigger on the handle
using these parameters. The general shape and dimensions are also designed to fit nicely
in one hand.

The envisioned drilling process is as follows:
• Select the suitable version of Goldrill tube based on anatomical measurement of
trachea.
• Attach the tube to handle, push the button to release the ratchet, and uncoil the by
adjusting the trigger.
• Insert the drill into the oral cavity, engage the ratchet and tighten the wire by pulling
the trigger (need not to hold it).
• Two ways to check the placement of drilling site: one is by touching from outside to feel
where the rigid steel tip is; the other way is by looking at the two “front sights” near the
catch to Goldrill tube—they indicate the direction strictly perpendicular to the drilling axis.

Figure 19.17
Tensile stress of tendon wire.