Page 100 - Flexible Robotics in Medicine

Flexible steerable manipulator utilizing complementary configuration 85

Figure 4.6
Distal connector segment, which will be coupled to a ball bearing on the distal end of the flexible
manipulator body and concurrently acts as a holder for a pair of forceps.

forceps. The control cable of the forceps (or end effector) passes through a lumen in the
center of the distal connector segment 6 12.

The method of fabrication of the ball bearings, hollow cylindrical segments, and the distal
connector is intended to be done by three-dimensional (3D) printing using 316L stainless steel.
Many commercial endoscopes and other medical equipment such as joint implants have
segments that are fabricated with 316L stainless steel. 3D printing using 316L stainless steel can
produce better mechanical properties with more refined microstructures, as there is a fast rate of
solidification. Also, this grade of stainless steel is more resistant to corrosion. Moreover, the
simplicity of the segments of the proposed manipulator will enable them to be easily 3D printed
without requiring much-supporting material or structure. It should be highlighted, however, that
the fabrication of the segments is not limited to this material and fabrication method.

4.2.1 Proximal control system

The flexible distal tip of the prototype is articulated using a proximal control system made
up of (1) an electronic actuation system with stepper motors, gears, and spools for the
driving cables; and (2) a control handle with a joystick to control the direction and
magnitude of bending, as well as buttons to open or close the forceps. The stepper motor is
engaged to the gears to provide higher power transmission efficiency, and the spools are
attached to the gears such that they rotate along with the gears.

The joystick is positioned on one surface of the control handle such that the operator can use
his/her thumb to actuate bending of the manipulator so as to orientate the forceps into a
position that facilitates the grasping of tissues. Upon movement of the joystick in a particular
direction, the microcontroller enables the rotation of the motor to reel in and thereby tension