Application and Mechanical Evaluation of Polyarylate Fiber Rope in Wire Drive Mechanism of Robotic Surgical Instruments

In this study, a polyarylate fiber rope, which is a high-strength synthetic fiber rope, is used in the wire drive mechanism of a multi-degree of freedom (DOF) robotic forceps to evaluate its mechanical practicability. Using a nonconducting material for the drive wire, different from typical use of metallic wires made of stainless steel and tungsten, a technology is developed to simplify the insulation structure significantly, decrease the diameter of the robotic surgical instrument, and lower its cost. In this study, first, a prototype of the multi-DOF robotic forceps equipped with a polyetheretherketone (PEEK) resin flexible wrist joint part with an external diameter of 5 mm is manufactured. The prototype is used to evaluate the assembling of a polyarylate fiber rope with a diameter of 0.34 mm in a multi-DOF mechanism and examine the endurance of the rope to mechanical motions under a single-use assumption. As fastening structures to assemble the rope – a crimp terminal using a hollow pipe and a thread knot – are examined individually by assembling them in the prototype robotic forceps and conducting strength tests of the tension generated by the drive. The test results show that the thread knot method exerts a stabler fastening strength than the hollow pipe method. However, a problem of the former is that the wire may break because of its strong contact with the edge of the hole of the wire guide. Subsequently, to evaluate the endurance of the rope to single-use operation motion, operation tests are conducted by implementing reciprocating bending motions of the flexible wrist joint part of the robotic forceps 1,000 times. The assembled rope endures the sliding within the flexible wrist joint part and the contact loading with the guide part and the fixed structure within the cartridge repeatedly. The endurance operation test results confirm that the drive transmission of the polyarylate fiber rope has sufficient mechanical endurance to 1,000 reciprocating bending motions of the PEEK flexible wrist joint part.