Design of the dullomatic: a mechanical follow-the-leader device

Abstract

Minimally invasive surgery (MIS) has several advantages over conventional surgery, including reduced damage to the body, less pain, lower infection risk, and faster recovery. However, MIS reduces the amount of space in which clinicians can operate within the body. This often forces them to work around delicate anatomical structures. A new type of instrument that can manoeuvre the body with snake-like movement, also called follow-the-leader (FTL) locomotion, could be a solution. A challenging design aspect of FTL instruments is to conserve the instrument’s shape accurately while the instrument propagates into or retracts from the body. This thesis presents a new device, called the Dullomatic, which can conserve 2D shapes and fits inside an instrument’s flexible shaft. The Dullomatic contains two adjacent mechanical shape memories which alternate between a flexible and rigid state, together forming a shaft. The device can be operated such that it conserves the shape and shifts the shape backwards as the device propagates forwards, or vice versa, to attain FTL locomotion. A prototype of this design was manufactured at a 2:1 scale containing 3 segments per shape memory. This prototype was evaluated by performing four FTL steps over a curved trajectory and measuring the position of the segments after each step. The results show that the device could be operated to accurately follow this path with FTL locomotion. Further research is required to enhance its user interface and investigate its potential for miniaturization. The Dullomatic forms an interesting addition in the field of FTL devices and might be able to aid in further reducing the invasiveness of surgery.