PALPABLE: Multi-sensing Tool For Minimally Invasive Surgery

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PALPABLE introduces a new generation of MIS (Minimally Invasive Surgery) tools: a novel tactile sensing probe as a palpation tool for identification and visualization of tissue abnormalities. MIS has several advantages (reduced tissue damage, postoperative analgesic requirements & blood loss, decreased hospitalization time, better cosmetic results), but there is limited or no visual, haptic, and tactile feedback in-situ, along with issues of tool dexterity. These issues can lead to accidental tissue damage. The probe (diam. 5mm, length 15-20mm) incorporates multiple sensing modalities and a thin, flexible, pneumatically actuated end-effector (3DOF, 180deg) with distributed sensors for distributed tactile sensing. The probe consists of photonic sensing elements and a sphere held at the end of a circular tunnel by a steady flow of air. The sphere is free to rotate in all directions and can move into the channel when pressed against the airflow. When rolling over tissue, the displacement depends on the tissue’s stiffness and is picked up by the optical fibre above it. Optical intensity variation in the sensing element is used to identify tissue stiffness variations. The principle of measurement used is extrinsic light intensity modulation provided through optical fibres. A non-planar photonics circuit (200µm waveguide, 8bit colour depth) for a haptic sensor array will be developed and interfaced with the probe; this circuit will be engraved on ultra-thin polymeric foils. The foil sensing elements are distributed around and along the probe for multiple sensor inputs for palpation (i.e., stiffness), distance and curvature that are then fused to provide the overall tissue condition. Using thin foils allows for ease of integration with the probe and a straightforward manufacturing process to enable low cost in large volumes. The end effector is made from disposable or sterilizable materials, both options will be explored for recyclability and reusability respectively.