Light Intensity-Modulated Bending Sensor Fabrication and Performance Test for Shape Sensing

Notable advancements in shape sensing for flexible continuum robot arms can be observed. With a keen interest to develop surgical and diagnostic tools that can advance further and further into inaccessible spaces along tortuous pathways, such as the human body, a need for the precise determination of the robot’s pose arises. Whilst there have been techniques developed that use external sensors to observe the advancing robot from the outside to determine its location and orientation in space, there is an observable trend towards using integrated, internal sensors to measure these positional parameters. Especially in the medical world with its tough requirements on robot size, e.g., catheter-type robots, most pose-sensing approaches to date make use of a technique called Fiber Bragg Grating (FBG). FBG sensors make use of fibers that are grated, and the amount of bending can be determined with an appropriate optical interrogator. Although these fiber sensors have been successfully employed to measure the deformation and through advanced signal processing the pose of continuum catheters, they have a major drawback which is their exorbitant cost. To address this issue a different design and fabrication process is proposed to produce an affordable shape sensor that is highly flexible and can detect bending. The method of operation involves a segmented flexible robot arm with three waveguides in a 120-degrees configuration. The segments are made of silicone elastomer with channels that encapsulate light propagating internally, with a photodiode and light-emitting diode (LED) embedded in each individual channel. The prototype was developed and characterized for strain, and bending response detection.