DNA-Helix Inspired Wire Routing in Cylindrical Structures and Its Application to Flexible Surgical Devices

In general wire-driven continuum robot mechanisms, the wires are used to control the motion of the devices attached at the distal end. The slack and taut wire is one of the challenging issues to solve in flexible mechanism. This phenomenon becomes worse when the continuum robot is inserted into the natural orifices of the human body, which inherently have uncertain curvilinear geometries consisting of multiple curvatures. Inspired by the unique characteristic of DNA-helix structure that the length of the helix remains almost constant regardless of the deflection of the DNA structure, this article proposes a new idea to design useful flexible mechanism to resolve slack of wires. Using modern Lie-group screw theory, the analytic model for length of helix wire wrapped around a single flexible backbone is proposed and then extended to a general model with multiple flexible backbones and different curvatures. Taking advantage of this helix type wire mechanism, we designed and implemented a flexible surgical device suitable for laryngopharyngeal surgery. The effectiveness of the proposed flexible mechanism is demonstrated through both simulation and phantom experiment.