Page 38 - Flexible Robotics in Medicine

Prototyping soft origami quad-bellows robots from single-bellows characterization 21

Meanwhile, another study explored a cylindrical robot functioning by peristaltic motion
with a specific practical application in colonoscopy [6]. The peristaltic motions utilize
shape memory alloy springs with air tubes along with silicone rubber skins, which provide
traction to aid the robot’s locomotion.
Another approach involved using origami to develop a crawling robot [7]. The design
coupled rotational and linear motion into the origami folding pattern so that the
structure could achieve broad stroke snapping motions from relatively small inputs
generated by a single motor. The major innovation of the study was their demonstration
of a numeral scheme for the origami folding that simplified their kinematic and force
analysis, eliminating the need for extensive finite element methods for the
computations.

When looking at existing cylindrical bioinspired robots, the basic types are the
inchworm and earthworm. The locomotion of the inchworm consists of arching the
central portion of the body in an omega shape and then flattening out for a progressive
crawling motion that utilizes friction. This type of motion is the basic, yet has the
potential to be versatile and adaptable [8]. The locomotion of the earthworm is a
peristaltic motion, where a similar peristaltic crawling motion is through sequential
contraction of different segments of its body length. This locomotion is unusual due to
the lack of a rigid skeleton and multilegged body to achieve more degrees of freedom
than the inchworm. By varying the stiffness of different parts of their body, they
can achieve bending, twisting, and deformation in addition to the standard crawling
motion [9].

However, the animal that is one of the frequently chosen as inspiration for various types of
robots is the snake, as it offers a wider variety of movements and degrees of freedom
compared to its tubular animal counterparts. The snake has a natural ability to cross
multiple types of terrain, navigating narrow spaces, as well as the winding nature of its
movement. These characteristics make the snake’s movement suitable for traversing the
narrow and tortuous colon.

A recent study [10] relevant to this project has shown significant progress in this field
of research. However, the main difference is that the study used kirigami instead of
origami, which involves cutting instead of folding of paper to achieve three-
dimensional (3D) structures. The difference in cutting compared to folding is the ability
to achieve stretchable and morphable structures that are based on the material’s tension
properties rather than limited by the maximum volume based on the material used. A
key result that the study managed to achieve was the success of their snake robot
prototype in imitating the ability of the snake to utilize their scales to aid their
movement. Designs using the principles of kirigami have advantages that are not easy
to attain based on origami. Another critical achievement [10] was using slight