Page 218 - Flexible Robotics in Medicine

Compliant bending tubular mechanisms with variable groove patterns 205

Figure 8.9
Stainless steel before and after bending.

after the bending force was released. However, stainless steel tube (Fig. 8.9) was not as
elastic and remained bent after the force was released.
The bending force was measured for both materials, and both, with the flexible drill, can
withstand more than 5 N bending force. However, when a maximum bending force is tested
with just the tubes alone, both tubes broke when more than 3.5 N force is applied. As our
prototype ideally only requires about 5 N force, using nitinol tube with fishbone-like design
1 seems possible.

8.4 Bending tube mechanism with modular sections

8.4.1 Goldfinger retractor inspiration

Made up of different sections held together by stainless steel cables, the Goldfinger
retractor (see Fig. 8.10) can bend at an angle, depending on how each section is
configured. The bending motion is controlled by tightening the stainless steel
wires inside the equipment. Each segment is designed in a way that the equipment
bends into the required shape when the wires are being tightened. Bending occurs
when the length of the guidewire is shortened, thus creating a pulling effect for the
bending motion.