ElastoSight: Miniature Tactile Sensors for Multimodal Force and Geometry Estimation in Robotic Intraluminal Palpation

Abstract

Contact-based evaluation of tissue biomechanical properties in intraluminal scenarios through robotic palpation is crucial for disease diagnosis. However, the real-time acquisition of distal information regarding the contacted tissue’s interaction state and physical characteristics remains challenging. As an emerging technology, endoscopic optical coherence tomography (OCT) has demonstrated remarkable capabilities in real-time visualization of three-dimensional (3D) microstructures and subtle lesions of luminal organs. Motivated by this, this work develops a novel miniature OCT-based tactile sensor named ElastoSight, enabling multimodal measurements of contact force and geometric deformation at micrometer resolution. Meanwhile, we propose a bistable snapping mechanism to mount PDMS films on OCT probes through mechanical assembly rapidly. Considering spherical contact as an example, we adopt the Hertz contact theory for contact-based calibrations on three configurations with varying film thicknesses, including 200 µm, 300 µm, and 400 µm. The results indicate that the force sensing performance complies with Hertz’s contact theory within the small deformation range and conforms to exponential contact in the large deformation range. Sensitivity analyses elucidate the impact of different film thicknesses on measurement stability and operation range. The maximum shape observation errors for all three configurations are also experimentally proved below 0.15 mm. The proposed ElastoSight exhibits broad applicability and brings new directions for future multimodal tactile sensors.