Page 226 - Flexible Robotics in Medicine

Compliant bending tubular mechanisms with variable groove patterns 213

Figure 8.20
Microlumen tubes with a bending radius of about 1.5 cm.

Simple groove cuttings are done using a heated blade to try and achieve a smaller bending
radius. Cutting is done on each alternate side. Upon testing for bending, the tubes quickly
broke into segments at the cutting. These polymers are challenging for flexible drilling, as
they cannot undergo much strain and fracture upon bending.

8.5.3 Three-dimensional printed prototype using Ninja Flex

The manipulator is 3D-printed using Ninja Flex. This 3D printing filament is a
thermoplastic elastomer that produces plastic parts, and therefore satisfies the requirement
for the manipulator to be flexible. This part can create and hold a bending of more than
90 degrees.
The drill tip is attached to the manipulator and is part of the bending mechanism of this
prototype. When the drill is being “pulled,” this tension causes the manipulator to bend
(Fig. 8.21).
The main limitation would be that drilling cannot take place for this prototype. This is
because the drill tip cannot be extended when drilling since tension must be applied to bend
the manipulator. Thus contact between drill tip and surface cannot be maintained. Drill tip,
therefore, should not be part of the bending mechanism in order to allow the extension of
the drill tip. Dimensional accuracy would be difficult to achieve with 3D printing of small
parts. As the requirement of this prototype is 4 mm in diameter, printing an
acceptable dimensioned prototype would be difficult.