Development of a Gel Urethra Model Simulator Using Agarose-PEG and Performance Evaluation of a Soft Growing Actuator for Urinary Catheter Insertion Assistance

This paper proposes a urinary catheter insertion assistance mechanism aimed at reducing pain and the risk of injury during insertion, as well as an agarose–PEG gel urethra model simulator for its performance evaluation. Conventional urinary catheterization has the drawback that friction against the urethral wall and impingement at curved sections can cause severe pain and tissue damage to patients. To address this, we focused on a soft growing actuator that can advance through a lumen without sliding its outer surface, and we developed a urinary catheter insertion assistance mechanism utilizing this actuator. In addition, we newly developed a gel-based urethra model simulator, made of agarose and PEG, capable of reproducing urethral length, diameter, curvature geometry, and Young’s modulus, and used it for performance evaluation of the proposed mechanism. Fundamental property tests confirmed that gel containing 2% agarose and 20% PEG achieved a Young’s modulus (~125 kPa) equivalent to that of the urethra and exhibited high toughness. In insertion experiments using the urethra model simulator, the proposed mechanism demonstrated stable extension and catheter traction even in models with curvature or straight-section stenosis. These results indicate that a urinary catheter insertion assistance mechanism employing a soft growing actuator has the potential to effectively reduce friction and alleviate pain inside the urethra.