A Millinewton Resolution Fiber Bragg Grating-Based Catheter Two-Dimensional Distal Force Sensor for Cardiac Catheterization

This paper presents the development of a novel 2-D fiber Bragg grating (FBG)-based micro-force sensing design for detection of catheter tip-tissue interaction forces. A miniature and symmetrical force-sensitive flexure-based catheter distal sensor has been prototyped, and four optical fibers inscribed with one FBG element each have been mounted on it for force and temperature decoupling and detection. The axial property of the tightly suspended fiber configuration has been utilized with a pre-tensioned force, and the embedded FBG element can be stretched and compressed to sense the force-induced and temperature-caused strain variations. The proposed configuration can achieve an improved resolution and sensitivity than the light intensity modulation-based approaches, and avoid the limitations closely associated with the commonly direct FBG-pasting methods, such as chirping failure and low repeatability. Finite-element modeling (FEM)-based simulation has been implemented to investigate the flexure performance and improve the design. The decoupling approach has been proposed based on the simulation results and implemented to separate and determine the force and temperature. The force-sensing flexure prototype has been calibrated to achieve a resolution of around 4.6 mN within the measurement range of 0 ~ 3.5 N. Both static calibration experiments and in-vitro dynamic experiments have been performed to prove the feasibility of the proposed design. The decoupling capacity of force and temperature will benefit its broad implementations in generalized intravascular catherization procedures.