Three-Dimension Tip Force Perception and Axial Contact Location Identification for Flexible Endoscopy Using Tissue-Compliant Soft Distal Attachment Cap Sensors

In endoluminal surgeries, inserting a flexible endo-scope is one of the fundamental procedures. During this process, vision remains the primary feedback, while the perception of tactile magnitude and location is insufficient. This limitation can hinder the clinician's efficiency when navigating the endoscope through various segments of the natural lumens. To address this issue, we propose a fiber Bragg grating (FBG)-based tissue-compliant sensor cap with multi-mode sensing capabilities, including contact location identification at the terminal surface and the three-dimensional contact force perception at the tip. The soft sensor cap can be affixed to the standard endoscope tip, like a distal attachment cap, for easy installation. Utilizing the relative contact location information, operators can adjust the steerable segment of the endoscope when transitioning from one segment of a natural orifice to a narrower segment, which may be obstructed by constricted lumens. A finite element analysis simulation and the corresponding calibration process based on learning-based approaches have been carried out. The FBG-based sensor can perceive the tip contact force and identify the axial contact location with high precision, where the force perception error is less than 3%, and the contact location identification accuracy is 98.8%. The experimental results demonstrate the potential of the proposed sensing mechanism to be applied in surgeries requiring endoscope insertions.