Three-Dimensional Catheter Distal Force Sensing for Cardiac Ablation Based on Fiber Bragg Grating

This paper presents a high-sensitivity triaxial catheter distal force sensor for cardiac ablation through the combined use of a force-sensitive flexure and fiber Bragg grating (FBG) sensing. A miniature force-sensitive flexure has been designed as the catheter tip, and it has an elliptical hinge with a symmetric structure for two-axial transverse force sensing and employs a pair of U-type beam slots above the hinge to sense the z-direction force. Five optical fibers embedded with an FBG element each have been integrated with this flexure to detect the force-induced strain on the flexure. Each fiber is configured as a tightly suspended status with its two ends fixed, ensuring to achieve an improved sensitivity. The theoretical force-deformation relationship has been derived, and the approach for decoupling force and temperature has been presented. Finite element modeling based simulations have been performed to support the parametric design and improvement of the flexure structure. Static calibration experiments demonstrate the excellent resolution values of 2.13 and 2.52 mN for both transverse directions within -1 to 1 N, and 23.12 mN for the axial direction within 0-2 N. The linearity, repeatability, and hysteresis errors have been characterized with less than 5.3%, demonstrating the stable performance. The force and temperature can be effectively decoupled and detected with a temperature less than 60 °C. Dynamic loading experiments at different spatial angles and in vitro experiments in a silicone aortic vessel phantom have been carried out to further validate the effectiveness of the proposed design.