Ring Reinforced Silicone based Steering Head for Endoscopy like Applications: FEM simulation, development and force characterization

Physically interactive applications like tissue sampling have become essential in present day minimally invasive endoscopy/colonoscopy applications. This calls for specialized steering heads with force exertion ability, still maintaining simplified actuation mechanisms having inherent softness and steerability. This article presents development of soft hyperelastic material (silicone) based pneumatically actuated steering head with improved performance achieved through O-ring reinforcements. The design attains omnidirectional bending operations as well as extension capability enabling needle insertion by the steering head. The ring reinforcement not only contains the bulging effect but also enhances extension ability and range of bending. Additionally, it improves stiffness, structural stability and force exertion capability. The presented work implements two layer design principle - the inner actuator is made from silicone of harder shore hardness followed by a thin outer layer of softer silicone, embedding the O-rings in between. The steering head has been designed iteratively through in depth Finite Element modeling and analyses after obtaining material models of silicones experimentally. The actuator has undergone detailed characterization through simulation for its workspace and blocked-tip force capabilities at various configurations. The characteristics have been experimentally validated on the developed prototype.