Page 122 - Flexible Robotics in Medicine

108 Chapter 5

5.2.1 Vacuum-actuated prototypes

An actuation mechanism relies on using suction to create negative pressure between the
skeleton and the skin, causing the structure to bend. Inspired by the articles cited
above, a vacuum-actuated (VA) prototype (Fig. 5.2) was conceptualized by taking
the modular design with different bending angles and the vacuum actuation method.
It has a V-shaped element model (Fig. 5.3) that creates a channel in the center for
the drilling wire and provides horizontal stabilization when bent. Furthermore, the
channel in the middle forms a vacuum during actuation and compresses the two halves
together (Fig. 5.4). This allows the walls to provide damping of drilling vibrations
because the walls have a slight yield when an outward force is applied and can absorb
vibrations.
The device was actuated by using a suction pump at the base of the device to create a
vacuum within the plastic bag skin, which caused the device to bend. It was able to achieve a
gradual 90-degree bend using two 45-degree hinges to enter the trachea smoothly and ended
with a final 90-degree sharp bend for bending the drilling wire toward the trachea wall.

The VA prototype included a notch on the right half of the module to fix a 2 mm
diameter tube under it. The tube had an inner diameter of 1 mm and was used for
securing the drilling wire to the right side of the module during bending. The latex bag

Figure 5.4
Vacuum-actuated prototype diagram (orange outer solid contour lines: latex bag, blue circle
concentrically enclosing the solid circle/dot: 2 mm tube, black solid circle in the middle of the
valley: drilling wire).