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Soft-bodied flexible bending mechanism with silent shape memory alloys 245

telescopes. These systems are used for prostatectomies and being motor-driven and cable-
actuated, which makes the entire system big and bulky.

In Ref. [36], a flexible tip made of a superelastic Ni-Ti tube with an outer diameter of
10.5 mm and can be bent up to 90 degrees during the operation inside the human body. The
Endo-Periscope [37] has a steerable tip with a diameter of 12 mm and can be moved through
six degrees of freedom with a bending angle of 125 degrees in each direction using a cable-
driven mechanism. The prototype [38] with a diameter of 4.9 mm is able to bend up to 100
degrees with two degrees of freedom is operated by four cables. Currently, there are very few
transnasal or transoral endoscopes in the market that can be actively controlled once in the
operation region compared to laparoscopic endoscopes. This could be due to the space
constraint in nasal procedures compared to laparoscopy procedures. The tentacle structure
succeeds in demonstrating that there is the potential of creating an endoscope with the
proposed approach with a diameter of 6 mm. Moreover, using SMA wires for actuation for
such devices translates to portability since SMA wires do not require motors or pneumatic or
bulky electric equipment. The prototype was fabricated using a soft lithography technique
using 3D-printed molds, which means a cheap and simple fabrication process.

10.5 Conclusion

In this work, a tentacle structure for transnasal endoscopic surgery is fabricated with a
combination of soft casting and 3D printing technology. SMA wires were selected for
actuation since it is a compact and efficient form of the actuator with high potential in
small-scale robotics. The fabrication strategy involved in producing a soft cast with a 3D-
printed mold was discussed, and steps taken to interface a joystick-controlled system to
control the tentacle structure were charted. The tentacle structure demonstrated to bend
8.2 24.5 degrees with an input current of 0.5 1.5 A. It also showed that the tentacle
structure could bend in all four directions with the same bending performance by actuating
different SMA wires in the tentacle.

10.5.1 Future works

There are many directions that can be taken to advance the current prototype. Firstly, there
is still space for development regarding the fabrication of the mold. Using better 3D
printing methods or plastic injection molding, the surface finish of the mold could be
improved, which would further improve the surface of the tentacle structure which can be
easy to slide the tentacle easily in the nasal cavity and nasopharyngeal cavity. The SMA
wires have a maximum contraction of only 5% of its original length (as per the
manufacturer’s datasheet), which makes it challenging to achieve more considerable
deflections in the tentacle structure. This can be overcome by adding additional