Novel Design of Mechanically Etched Concentric Tube Robot with Advanced Stability and Workspace

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Surgical robotics have provided surgeons with additional dexterity, precision and control to perform procedures more accurately and efficiently. However, the smallest commercial surgical robots range between 5mm and 8mm where they are too large for procedures in neurosurgery and trans-oral repairs through a single incision or burr hole. Industry and research groups have attempted to build smaller diameter cable driven discrete jointed systems but there are fundamental challenges in the mechanisms and materials which are limiting factors. A novel approach is use a "continuum" robotic manipulator where the manipulator is a continuous material that can be actuated for tip control. For millimetre-sized tools, we have proposed an approach to use Nickel Titanium (Nitinol) shape memory alloys that are thermally shape set where they are assembled in a concentric tube robot (CTR). By rotating and translating each tube, one is able to control the tip in Cartesian space. CTRs provide sufficient dexterity and stiffness for surgical tasks but there are limitations in their workspace due to "torsional wind-up". The "torsional wind-up" is caused by friction between the inner and outer tubes where the distal tip rotation may not match the proximal tip input. As this "wind-up" increases, it causes a point of instability and leads to unwanted snapping motion. To overcome the torsional instability, our research will study and optimize techniques to mechanically etch various patterns on Nitinol tubes to increase the linear response of the torsion of Nitinol tubes. Preliminary results have shown the simple etching patterns can increase the linearity and remove the "snapping" motion. There are 3 main points to the hypothesis: 1. Etching will create cellular tubes with increased torsional stability, 2. Optimized tubes will have reduced wind-up at lengths and curvatures for surgical tool and 3. Etched tubes can be implemented for a CTR to perform neurosurgery and trans-oral procedures. For this work, this project will involve 2 PhD level graduate students, clinical fellows and a research engineer who will be trained to be experts in the area of continuum manipulators, mechanical optimization and surgical tool development. This research will be conducted at the Centre for Image Guided Innovation and Therapeutic Intervention (CIGITI) at the Hospital for Sick Children. CIGITI is leading image guided research centre where its staff and students have received numerous international, national and provincial awards in the area of surgical robotics research.**