Design of a Grasping Mechanism for a Friction-Based Transport Mechanism

Abstract

This report describes the design of a wire rope based grasper for a tissue transport mechanism based on friction including means for operation. The previous transport mechanism design had no mechanism to transfer tissue into the lumen to be transported. To create the grasper, the wire ropes were plastically deformed to bend outward, creating the open shape of the grasper. A sheath consisting of magnets, springs, and a shrink tube can be slid over the plastically deformed section, straightening the wire ropes. This closed the grasp to constrain tissue. Operation was done by four finger handles, two on the main device and two clamped on the slidable sheath with magnets. Springs were used to make the passively hold the grasper in closed position, making it voluntary opening. To maintain the shape of the grasper, wire ropes were soldered together at the grasper tip, constrained in the sliders of the transport mechanism and wire rope guides were placed to the side of the magnets. After constraining the tissue, transfer into the lumen was done by actuating the transport mechanism. Gelatin phantom tissue samples were used to test the functionality the of the grasper. Results show successful constraining of 3mm, 4mm, 5mm spheres as well as a cylinder of 4mm with a length of 6.5mm. The spherical samples were all successfully transferred into the transport mechanism. The cylindrical sample was successfully transferred when inserted in axial orientation, but three out of six samples failed when insertion was perpendicular to the transport mechanism. Tissue samples were successfully grasped from a surface in three different orientations and the grasper was tested with the transport mechanism in a bend to test if no original functionality was lost. This grasper allows for a step towards a new surgical instrument.