Design and Experimental Validation of a Fiber Bragg Grating-Enabled Force Sensor With an Ortho-Planar Spring-Based Flexure for Surgical Needle Insertion

This paper presents the development of a novel and high-precision Fiber Bragg Grating (FBG)-based sensor for the measurement of insertion forces during the needle puncture procedure. The proposed sensor mainly comprises two compact orthogonal planar springs connected in a parallel arrangement, one suspended FBG optical fiber and a hand-held sensor frame. Two orthogonal planar springs with curved limbs have been utilized to design the force-sensitive flexure with an excellent linear force-displacement relationship along the axial direction. The employed optical fiber has been arranged along the flexure’s central line, and it is tightly suspended under a pre-tension force with its two ends glued. This two-point pasting configuration can attain improved sensitivity and resolution and avoid the drawbacks of chirping and low repeatability. Finite element modeling (FEM)-enabled simulation has been implemented for design optimization to further advance the sensor sensitivity and performance investigation. The sensor’s axial sensitivity has been increased in the condition when the radial crosstalk decreased. The proposed sensor has been prototyped and calibrated to achieve a high resolution of 1.5mN within [0, 6N] and an excellent linearity with a small linearity error of 0.5%. This design can be conveniently customized to achieve adjustable measurement range and force sensitivity, which has been validated by the further simulation sensor version with a resolution of 4.9mN within [0, 20N]. In-vitro puncture experiments on silicone phantoms, artificial venipuncture simulation module and eggshell membrane, and ex-vivo puncture experiments on porcine liver and porcine aorta have been implemented to validate the effectiveness of the presented sensor design.