Page 59 - Flexible Robotics in Medicine

Cable-driven flexible endoscope utilizing diamond-shaped perforations: FlexDiamond 43

nondeformable element would have 6 degrees of freedom (DOF): 3 translations and 3
rotations. Such individual elements can be connected in a fashion where the individual
localized deflection can be superimposed to achieve a macroscopic deflection in the
manipulators bending region. Innovations of such rigid typically include improvements in
bending angles, reduction of segments to achieve bending, more sensitive controls in
bending, and better navigation of complex pathways. Flexible manipulators function in
similar principle but they experience more challenging precise controls of deflection due to
innately more challenging restriction requirements. For example, rigid endoscopes seldom
have to include torsional analysis while flexible endoscopes torsion can affect bending
controls depending on the flexibility of the endoscope.

Flexible manipulators, unlike rigid endoscopes, can be further defined into continuum and
segmented. The most viable option of a rigid continuum endoscope was determined to be
concentric precurved tubing but could experiences problems with buckling. Segmented
flexible endoscopes are similar to rigid endoscopes except that the segments and joints can
be flexible. The prototype is defined as being a continuum rather segmented due to the
definition of segmentation. There have to be distinct elements connected via joints wherein
such elements are similar if not identical to each other. A key feature in most continuum
flexible endoscopes is that the deflection of the bending region is not a superposition of
summative segments but somewhat controlled buckling of the bending region. The control
of buckling usually refers to the method to control and/or define flexibility variations along
the longitudinal axis of the tube.

The manipulation of flexibility can be done depending on if it is a single tube or multiple
concentric tubes. For multiple concentric tubes, the tubes can vary rigidity such as having
more inner tubes or have specific placement of inner tubes to define bending regions and
rigid regions. This is based on the concept that varies the second moment of the area along
the longitudinal axis of the tube. The concentric tubes can vary such as in having various
combinations of flexibility and even members that can be compressive and/or tension
members. For a single tube, the variation will be to manipulate the flexibility of that tube
along its longitudinal axis. This is achievable in many ways such as material choice, torsion
manipulation, and modification of a structure to induce bending regions via the introduction
of a plurality of incision in the material along its longitudinal axis. Specific types of cuts in
the material can increase or decrease the flexibility of one region with respect to another.
Classic examples utilize a helical cut to induce flexibility and another concentric tube to
increase or decrease the flexible element. Tapering of the tube’s thickness to change the
second moment of area is noted to be a viable approach by prior arts for single continuum
flexible tubes. The prototype utilizes explicitly diamond cuts on the material to produce a
stent-like configuration in the bending region, which has not been employed in any other
similar incision designs typically of rectangular slots. Specifics to the details of the design
will be discussed further.