Page 46 - Flexible Robotics in Medicine

Prototyping soft origami quad-bellows robots from single-bellows characterization 29

Figure 2.5
Comparison of different attempts of folding with varying diameter and material.

unprecise folding. Hence, the prototypes were sized at 15 mm in diameter, preliminarily,
while preserving the precision of creasing and folding. Fig. 2.6 showshow theremoval
of material due to etching resulted in increasing flaking along the edges of the creases
upon folding.

To actuate the prototype with pneumatics, the surface of the folded bellows needed to be
coated to make the prototype airtight since the paper is naturally porous. Silicone rubber,
specifically Smooth-On Dragon Skin, was used for this coating. The material requires the
addition and mixture of two parts (silicone polymer and a catalyst). A thin layer of the
mixture seals the surface of the bellows units after curing.

Once the bellows units were cured, they were assembled into a four-bellows design, as seen
in Fig. 2.3 before they were inflated to test the movement patterns that could be achieved.
The bellows design has a gap between adjacent bellows units, which is for the inclusion of
endoscope for the future application for colonoscopy. The endoscope has a camera tip and
thus is limited compared to an actual endoscope and not representative of the multiple
instrument channels and tools involved in medical colonoscopies.

2.3.4 Colon phantom

For ease of experiments in the earlier stages, the model of the colon used polycaprolactone

(PCL), a moldable material once heated past a relatively low melting point of 60 C, which
will harden back to its plastic form once it cools back down to room temperature. Future
work will investigate using CAD that is anatomically accurate and complete to 3D print a
full model of a colon. However, for early-stage prototyping experiments, this method was
not chosen due to time duration and difficulty in 3D printing and removing excess material
for an accurate hollowed interior.