Design Optimization and Characterization of a 3-D-Printed Tactile Sensor for Tissue Palpation

Manual palpation is a crucial medical procedure that relies on surface examination to detect internal tissue abnormalities, heavily reliant on healthcare professionals' expertise and tactile sensitivity. To tackle these issues, smart palpation systems based on electrical or optical sensors have been developed to perform quantitative tactile measurements, crucial for identifying various solid tumors, including breast and prostate cancer by assessing tissue mechanical properties. In this context, fiber Bragg gratings (FBGs) are emerging as a an ideal candidate for tactile sensing due to their advantages (e.g., high metrological properties, multiplexing capacity, and easy packaging). This study explores the benefits of FBG and 3-D printing to develop a tactile sensor for tissue palpation. First, an optimization of the design of the sensing core of a previously developed probe was conducted through finite element analysis. The novel structure addresses the primary limitation of the previous solution, where nonuniform strain distribution on the encapsulated FBG causes compression on the grating with high risk of bending and breakage. In contrast, the modeled geometry ensures FBG elongation during tissue palpation. A 3-D printing and characterization of the proposed solution was carried out to investigate the response of the enclosed FBG when pushed against different materials showing promising results in discriminating tissues according to their mechanical properties: the more rigid the indented substrate, the higher the sensor output. This property will be fundamental for enhancing early tumor detection through superficial tissue palpation, advancing the efficacy of prevention measures.