Multi-Sensing System Based on Fiber Bragg Grating Technology in Variable Stiffness Catheter for Temperature and Force Measurements

This study focuses on the design, development, characterization, and feasibility assessments of a multi-sensing system based on fiber Bragg grating sensors (FBGs) to monitor force and temperature within a shape-memory polymer (SMP) guiding catheter. SMPs possess the unique ability to transition between rigid and flexible states based on user's needs, making them invaluable resources in minimally invasive surgery (MIS), as they allow for improved flexibility and adaptability even in anatomically complex areas. As the softening action takes place by heating the SMP, temperature monitoring is a key factor in determining the SMP flexibility. By embedding FBGs, it is possible to get real-time feedback, ensuring that the catheter achieves optimal flexibility. Additionally, this study tackles a significant hurdle clinicians face: the absence of tactile feedback. Sensing variations in tissue properties is essential for achieving reliable performance. For this reason, this work introduces a novel approach by equipping a biopsy needle with FBGs capable of measuring both temperature and force. The thermal charac-terization performed to assess the thermal sensitivity (ST) of the FBGs used for temperature measurements revealed a mean ST value of 0.029 nm- 0 C -1 • Additionally, temperature measurements during thermal activation demonstrated the suggested system's ability to track temperature variations along the SMP catheter length (with a maximum of 68 0 C). Lastly, compression tests were performed to evaluate the multi-sensing system's capacity to distinguish between compounds with varying stiffness (Drag-onSkinl0 and 30). The observed greater force values in the tests involving DragonSkin30 (2.3 N), compared to DragonSkinl0 (up to 1.3 N) for identical displacements, underscore the capability of the proposed system to discriminate between materials based on their stiffness levels.