FBG-based Triaxial Contact Force Sensor with Segment-by-segment Sensitivity Separation Method Using a Single Fiber

In the treatment of atrial fibrillation (AF), ablation stands as the foremost therapeutic strategy. Crucial to the success of ablation is the creation of transmural injuries in the cardiac tissue. The integration of a force sensor at the distal end of the catheter holds the potential to accurately quantify the extent of ablation-induced damage, thereby significantly enhancing the success rate of the procedure. This article introduces a novel isotropic three-axis force sensor, leveraging fiber Bragg grating (FBG) technology. A unique segment-by-segment sensitivity differentiation technique is implemented to decouple three-axis forces. This innovation empowers the sensor with adaptable stiffness adjustments in all spatial directions and robust elastomeric integration. Moreover, the utilization of a single optical fiber substantially enhances the overall flexibility of the catheter. The sensor's structural integrity is rigorously validated numerically and experimentally. Calibration of the sensor is performed using both linear and nonlinear models. Results demonstrate that the designed sensors meet technical specifications, achieving a resolution of less than 1 g. In terms of accuracy, the nonlinear model exhibits superior performance. Root-mean-square errors for sensors operating within lateral [-1 N, 1 N] and axial [0 N, 2 N] ranges are all within 1.2% of the full scale.