Disposable FBG-Based Tridirectional Force/Torque Sensor for Aspiration Instruments in Neurosurgery

This paper presents a disposable fiber Bragg grating (FBG) based tridirectional force/torque sensor mountable at the end of the tip of the aspiration instruments for detecting instrument-tissue interaction force/torque. The sensor utilizes an inexpensive three-dimensional (3-D) printed elastomer with an annular diaphragm, which is sensitive to axial force (Fz) and torques (Mx and My). Four suspended optical fibers inscribed with an FBG each have been fixed on two ends of the elastomer to simultaneously sense and decouple force/torque-induced diaphragm deformation. The associated sensing theoretical model and force-torque decoupling principle with temperature compensation have been derived. Calibration experiments demonstrate a high resolution of 8.8 mN within the range of 0-2 N for the axial force detection. Dynamic performances of the designed sensor have been evaluated in comparison with the commercial force sensor. The average relative errors of force/torque components are less than 4.4% of full-scale range. The maximum temperature drift-caused errors of the force/torque components within the range of 30 °C-45 °C are -0.1340 N, 0.0084 N·mm, and 0.0300 N·mm, respectively. In vivo experiments on a cadaver head have been performed to further validate the feasibility and effectiveness of the designed sensor for real-time monitoring of the interaction force.