A Novel 6-DOF Flexible Instrument With High-Resolution Three-Axis Force Sensing Unit for Endoscopic Submucosal Dissection

Gastrointestinal (GI) cancers have a significant impact on human health due to their high mortality rate. In endoscopic submucosal dissection (ESD), surgical instruments require both sufficient flexibility and operational freedom, as well as a precise and sensitive force sensing function to avoid the risks associated with insufficient or excessive contact force between the tip and the tissue. These requirements pose significant challenges to the development of flexible surgical instruments with force sensing capabilities. In this work, we propose a 6-DOF flexible instrument based on tendon-actuated stacked-buckle joints. This instrument can achieve large hemispherical and cylindrical workspaces with a radius of 27 mm, and the measured tip positioning accuracy of the continuum is better than 0.36 mm. In addition, a fiber Bragg grating (FBG)-based three-axis force sensing unit is integrated into the distal end of the electric-knife instrument. The calibration experiment shows that the flexible instrument operates under three-axis force with high resolutions of 0.169, 0.172, and 0.398 mN for Fx, Fy, and Fz, respectively. The dynamic performance and temperature decoupling algorithm indicate that the proposed FBG sensing mechanism can accurately detect three-axis force. The ex vivo swine stomach ESD experiment has demonstrated the clinical application potential and practicality of the instrument.