A High-Resolution Triaxial Catheter Tip Force Sensor With Miniature Flexure and Suspended Optical Fibers

This article reports a miniature, high-resolution fiber Bragg grating (FBG)-based triaxial force sensor to detect the catheter tip-tissue interaction forces. This sensor counts on a delicate three-dimensional-printed flexure comprising a cylinder with an inner elliptical cavity for detecting lateral forces and a hybrid elastomer to enhance axial elasticity for improving z-directional force sensitivity. Four suspended optical fibers inscribed with FBG each are deployed inside the flexure. Such configurations are designed to maximize the decoupling among three force components, achieve temperature compensation, and raise the sensor's robustness under biofluid-filled environments. The sensor characterization results indicate a high resolution of 0.52 and 0.64 mN for both lateral forces within -0.8 to 0.8 N and 0.63 mN for axial direction force within 0-0.8 N. Validation with dynamic loadings along different azimuth angles shows that the sensor can provide a high-accuracy measurement of three force components with an rms error of less than 3.00%. Temperature-induced errors for force detection are considerably alleviated, showing less than 6.5% in the range of 25 °C-50 °C. Ex vivo experiments on a swine heart further validate the performances of the designed sensor.