New pneumatic rubber actuators to assist colonoscope insertion

Inserting an endoscope into colon requires very technical procedure and it is difficult in some cases even for experienced doctors. Although active colonoscopes have been researched, these instruments are still in the development stage. Mechanisms for this application are required to be soft enough not to injure the colon wall and being deformable enough to adapt to the curves of the colon. In addition, the mechanisms must generate distributed force adequate for traveling. These requirements are difficult to be satisfied using conventional mechanisms and actuators. We have designed and developed two types of new driving mechanism using pneumatic rubber actuators and made their feasibility tests. One mechanism is "thin tube wave generator": introducing pulse pneumatic flows to a thin rubber tube causes traveling deformation waves on the tube surface, which drives an object placed on the tube. The other mechanism is "round bubbler": A rubber tube which has four chambers in it is wound around the colonoscope to cause traveling deformation waves on the scope surface by sending pneumatic pressures to each chamber sequentially. In this paper, first, we discuss the driving mechanisms, pneumatic control systems, and basic characteristics of these two mechanisms. Then, based on the basic experimental discussions, we fabricated special rubber mechanisms to fit around a conventional colonoscope, and conducted insertion experiments using an intestinum model and an existing colonoscope under various conditions. The experimental results are very promising.