A 3D-printed sensing element based on fiber Bragg grating technology for grasping force measurement in surgical forceps

This study introduced a 3D-printed sensing element based on fiber Bragg grating (FBG) technology to measure grasping forces when integrated into surgical forceps during minimally invasive surgery (MIS). Its design mainly consists of an octagonal-shaped structure with a single FBG suspended within, the first to use fused deposition modeling technique in this application scenario. This novel solution allows improving the design customization and the structural robustness of the proposed sensing element. A finite element model was developed to study the mechanical behavior of the structure under transversal force (F) values experienced during grasping. Thermoplastic polyurethane material as printing filament enhanced the deformation capabilities of the sensor, thereby optimizing its response to F as evidenced by the value of sensitivity to F (i.e., 0.11 nm·N⁻¹). Additionally, the sensing element exhibited a low hysteresis error (always below 14 %). Tests in controlled conditions confirmed the sensor capability to discriminate materials with different stiffness. Furthermore, the sensor was used as the sensing core of a surgical forceps prototype and tested during ex vivo experiments on hepatic, myocardial and spleen tissues simulating a MIS environment. The system was able to measure F during tissue grasping and the real-time feedback improved the tissue holding stability, important for reducing tissue damage risk during MIS procedures.