Development of a Fiber Bragg Grating-Enabled Clamping Force Sensor Integrated on a Grasper for Laparoscopic Surgery

This paper presents a clamping force sensor based on fiber Bragg grating (FBG) to provide interaction force feedback for laparoscopic surgery. The proposed sensor mainly consists of a force-sensitive clamping flexure and a tightly suspended optical fiber with an FBG inscribed. The force-sensitive clamping flexure utilizes a bridge-type structure with an excellent load-bearing capacity and anti-interference ability to linearly convert the vertical force or displacement input exerted on the grasping surface into translational deformation along the flexure central line. The FBG fiber is arranged along the flexure central axis to sense the vertical force-induced horizontal strain. This two-point pasting configuration can achieve a uniform fiber strain distribution and an enhanced sensitivity. This assembly arrangement produces a linear relationship between the applied vertical force and the force-induced horizontal strain value sensed by the FBG. The force sensitivity remains the constant and it less affected by the grasping positions due to the high stiffness and deformation conversion, overcoming the difficulty that the traditional clamping force sensor designs are sensitive to the grasping position due to the variable grasping positions and areas on the soft tissues during clamping. The finite element method (FEM)-based simulation has been utilized for design optimization and performance investigation to guide the sensor design. The simulation sensitivity values have been determined as a close value of 52pm/N regarding the three different grasping positions at middle, left and right parts. The optimized sensor design has been integrated into a manual surgical grasper and achieve experimental sensitivity values of 56.2pm/N, 51.1pm/N and 47.5pm/N for the three different loading positions within [0, 10N]. Both dynamic loading experiments and clamping experiments on ex-vivo tissues and in-vivo animal for tissue resection were implemented to validate the effectiveness of the proposed design.