Page 242 - Flexible Robotics in Medicine

CHAPTER 10

Soft-bodied flexible bending mechanism

with silent shape memory alloys aiming for

robotic endoscopy

Manivannan Sivaperuman Kalairaj, Tan Ze Feng and Hongliang Ren
Department of Biomedical Engineering, National University of Singapore, Singapore

Transnasal endoscopy is performed with small diameter scopes through the nasal passages
and nasopharyngeal cavity to explore any abnormalities in the nasal canal. The scopes are
either flexible or stiff, and some have the ability to bend based on proximal actuation,
mostly cable-driven. In this project, we design and fabricate a shape memory alloy (SMA)
actuated soft tentacle structure of a 6 mm diameter that can carry an endoscope camera and
navigate the nasal passages and nasopharyngeal cavity by proximal manipulation. We show
the fabrication strategy of combining the 3D printing technology and soft casting along with
the assembly of SMA wires to fabricate the working tentacle structure. We also show the
interface of the SMA wires in the tentacle structure to a joystick-operated microcontroller
to control the bending of the tentacle structure. We design the molds and fabricate using 3D
printing technology and the soft cast with a silicone elastomer as a passive element with
SMA wires as an active element. The bending angle of the tentacle structure is controlled
by both joystick and input current to the setup. The tentacle structure demonstrated to bend
8.224.5 degrees with an input current of 0.51.5 A. The tentacle structure can bend in all
four directions with the same bending performance by actuating different SMA wires in the
tentacle. The softness of the silicone elastomer will aid in the comfort of humans without
causing tissue damage.

10.1 Introduction

A minimally invasive surgery (MIS) uses specialized techniques and instruments like
miniature cameras and sophisticated fiber-optic video equipment, and sometimes image
guidance or ultrasound technology to access the operative region. Rigid tools lack the
optimum for the exploration of narrow crevices or cavities in applications such as head and
neck surgery. To overcome these limitations, research and development are conducted on

Flexible Robotics in Medicine.
DOI: https://doi.org/10.1016/B978-0-12-817595-8.00010-9 231
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