Tutorial: Nitinol and Tungsten Tendon Attachment Techniques for Steerable Continuum Robots

Minimally invasive surgery (MIS) has proven advantageous over open surgery in reducing patient trauma, complications, and time in the hospital. However, the small incisions required for MIS inhibit maneuverability and access to the surgical site. Dexterous robotic instruments are a promising area of research to overcome these challenges in MIS. Tendon-driven continuum robots have shown potential to expand surgeon capabilities for operating within confined spaces and with minimal injury to the patient. For many procedures, miniaturized devices on the micro- and meso-scale are desired to access confined areas within the body and enable sufficient maneuverability. These robots are a topic of active research, and the fabrication of such miniaturized mechanisms remains challenging. To address these challenges, this paper provides a tutorial which outlines and evaluates various methods for attaching tendons in micro-and meso-scale robotic joints. Attachment techniques including bonding and plate mechanisms are used to assemble nitinol and tungsten tendons within both micro- and meso-scale samples. For micro-scale robots, samples less than 1 mm in diameter are used to evaluate the strength, repeatability, and actuation within a continuum robotic guidewire. For meso-scale robots, such as 1.93 mm diameter neuroendoscope tools, tendon placement is achieved using stainless steel and 3D-printed plates. Furthermore, the effects of solder and epoxy knot reinforcement are studied. Detailed procedures for attachment methods are provided, and the strengths and limitations of the tendon materials and attachment methods studied in this paper are highlighted for specific applications.