Preliminary Study of a Spring-Based Miniature Extensible Manipulator for Bronchoscopic Steering

Bronchoscopy is widely used as a minimally invasive diagnostic and therapeutic modality for early screening of bronchial diseases. To face the complicated airway structure and gradually decreasing bronchial diameter with increasing generation, the bronchoscope with enhanced steering capability is more competent. In this paper, a spring-based miniature extensible manipulator is proposed as the active bending segment for the bronchoscope based on the detailed problem statement about the steering ability. The manipulator, which takes advantage of the extension of the compression spring, features a simple structural design, offset neutral bending plane and extensibility. The associated kinematics based on the piecewise constant curvature model are presented in detail. To validate the concept, a manipulator prototype with an outer diameter of 4 mm and the custom actuation device with a constrained mechanism for the driven rod is fabricated. Several experiments including motion validation, kinematics validation, and steering capability validation are performed, and the results indicate that the proposed manipulator system is feasible and has the potential to improve bronchoscopic steering capability and to further improve diagnostic yield.