Design, fabrication and metrological characterization of a 3D-printed tactile sensor based on fiber Bragg technology for breast palpation

In the last decades, fiber Bragg grating (FBG) sensors have become increasingly prominent for biomedical applications, thanks to their several advantages, like lightweight, electromagnetic interference immunity, high sensitivity, and spatial resolution. Recently, FBGs have shown a relevant potential in tissue palpation, including breast examination, which is a crucial preliminary test for detecting possible tumor masses. However, traditional methods still rely on the examiner's subjective assessment, revealing the need for sensorized devices to detect tissue stiffness variations and enhance test accuracy. Although several tactile probes have been proposed for tissue palpation, most of them are essentially based on piezoresistive, capacitive, and piezoelectric sensors. The FBG technology is mainly used for invasive tissue palpation during minimally invasive surgery (MIS). So far, to the best of the authors' knowledge, only one 3D-printed tactile probe was developed by combining FBG potentials with those of 3D printing to overcome the limitations of previous systems.This work focused on the design optimization of the FBG-based sensor of a previously developed tactile probe. In more detail, a reduction of its dimensions by 25% was pursued. This reduction is crucial for enhancing spatial resolution and sensing element numerosity, which are essential for the detection of lesions at their early stage. The work includes a detailed description of the design process, incorporating finite element analysis to model the sensor response. Then, the sensor was fabricated, and its metrological characterization was carried out to investigate its response to force. The promising results will drive further size reduction and an increase in the number of sensing elements, paving the way for enhanced tactile probing capabilities.