A miniature fiber Bragg grating-based contact force sensor with parallelogram hollow slot and reduced-diameter structures for minimally invasive surgery

To tackle the loss of tactile perception in minimally invasive surgery (MIS) and the challenge of simultaneously achieving miniaturization, high sensitivity, and lateral-force resistance in existing one-dimensional optical fiber force sensors, this paper presents a miniature contact force sensor. The sensor is based on a Fiber Bragg grating (FBG) integrated with a novel staggered parallelogram hollow-slot structure. The sensor features an ultra-compact design with an outer diameter of only 1.3 mm and a length of 10 mm, demonstrating significant miniaturization compared to the majority of existing sensors. The hollow-slot structure not only enhances the axial strain concentration effect, thereby elevating the axial sensitivity to 415.9 pm/N, but also endows the sensor with robust resistance to lateral forces. Meanwhile, the reduced-diameter structure effectively improves the overall structural stiffness. A force-temperature decoupling mechanism is established through a dual-FBG configuration, effectively eliminating the impact of environmental temperature fluctuations on the accuracy of the measurement. Finite element simulations and comprehensive experimental validations—including static calibration, dynamic response evaluation, temperature calibration, lateral force resistance comparison, and simulated palpation experiments—demonstrate that the proposed sensor offers high sensitivity, excellent linearity, and real-time responsiveness, thereby meeting the requirements for precise low-magnitude force sensing in MIS.