An FBG-Based Soft Wearable Device for Force Monitoring During Palpation

Manual palpation is a diagnostic procedure commonly used to assess tissue stiffness and to detect abnormal masses such as lesions or enlarged lymph nodes. In this context, monitoring the force (F) exerted during the contact between the clinician’s fingers and the patient’s body can provide quantitative information to support clinical evaluation, reducing subjectivity and improving diagnostic reproducibility. This study presents a soft wearable device (SWD) designed to be worn on the clinician’s index finger for real-time monitoring of F during palpation. The system integrates a fiber Bragg grating (FBG) optical sensor, particularly suitable for this application due to its compactness, flexibility and high metrological performance. The SWD was fabricated using a skin-safe soft silicone matrix to ensure comfort and preserve the clinician’s natural tactile perception. Following the fabrication, the system underwent metrological characterization to evaluate its response to known F variations. Results showed a quasi-linear relationship between the SWD output (ΔλB) and F in the 0 N – 6 N range, typical of manual palpation, with a sensitivity of 0.040 nm/N and excellent repeatability under loading-unloading cycles. Finally, a real palpation test was carried out by a clinical operator on three healthy volunteers to assess the device performance under realistic conditions. The device provided stable and repeatable responses consistent with the applied F, with clear signal transitions corresponding to the onset and release of palpation. The clinician reported no perceptible alteration of tactile feedback, confirming the comfort, stability, and practical usability of the SWD during real palpation tasks.