Study On Flexible High Frequency Surgical Electrode

High frequency electrosurgical knife was used in neurosurgery earlier.With the improvement of medical level,high frequency electrosurgical knife has been widely used in clinical surgery.Especially with the rapid promotion of laparoscopic surgery,the advantages of high-frequency electric knife,such as less bleeding during operation,short recovery period after operation,greatly shortening the operation time and alleviating the pain of patients,have been recognized by doctors and patients.However,the basic properties and phenomena of high frequency electric knife and the formation and adhesion mechanism of surface adhesives are not clear.And the traditional electrode shape is flat knife or pre-bending electrode.It is very difficult to change the bending shape of the electrode according to the need of operation,which increases the difficulty of operation and medical risk.The traditional surgical instruments can’t meet the medical needs of the market.It is urgent to develop a free bending,rotation and stretching surgical instrument.The development of new surgical instruments and the study of the bending forming properties of electrodes are of great guiding significance for the development of flexible surgical electrodes and instruments.In this paper,the effects of electrode thickness of 304 stainless steel,cutting rate and cutting power on electrode cutting temperature,thermal damage and surface adhesion quality were studied.Performance testing was carried out by means of Fourier infrared spectroscopy and adhesion force measuring device,and the composition and adhesion mechanism of adhesives were analyzed.The bending life and bending phenomena of molybdenum electrode and rare earth molybdenum alloy electrode after different bending modes were compared.The bending characteristics and fracture mechanism of electrodes were studied by means of hardness tester,scanning electron microscope and universal material testing machine.The main conclusions include the following points:(1)Cutting temperature is proportional to electrode thickness,cutting rate and cutting power.The quality of adhesives on the electrode surface increases with the increase of cutting power,and the area of tissue thermal damage increases with the increase of electrode thickness and power.The 304 stainless steel electrodes with bending force of 2.8N and thickness of 0.5mm can meet the requirement of service under the condition that the electrode thickness is as thin as possible.On the premise of satisfying the requirement of electric cutting,the power and speed of electric cutting should be as small as possible.(2)Micron-sized particles and muscle fibers were formed after the muscle tissue fluid was heated and ruptured,and the particles were continuously concentrated on the surface of the electrode.The adhesives adhering to the surface of the electrode are still protein.The adhesives denatured and carbonized because of the high temperature of the electrode,resulting in the decrease of the functional groups of the adhesives at the working positions of the electrode.(3)The micro-melting of 304 stainless steel electrodes under local high temperature leads to the increase of the adhesion area between the adhesives and the electrodes.Moreover,there are elements enrichment and diffusion phenomena between the adhesives and the edge of the electrode,which leads to the increasing law of the adhesion force from the end of the electrode to the front end,and the maximum adhesion force is more than 130 MPa.The molybdenum electrodes with high temperature resistance were not found to be micro-melted during the electrochemical process,and the working temperature of the electrodes and the thermal damage to the tissues were less than 304 stainless steel electrodes.(4)The springback and work hardening of molybdenum wire exist in the bending process.The springback angle increases with the increase of bending angle,and the hardness at the bending point increases with the increase of bending times.The formula for fitting the actual bending angle after mechanical bending at 30,60 and 90 degrees are obtained as follows: Y = 0.9633x-8.56°.During the bending process,the tensile stress on the outer side and the compressive stress on the inner side of molybdenum wire.Under the action of compressive stress,grain warping and warping position become the source of crack initiation or the optimal path of crack propagation.As the neutral layer moves inward,the stress area of molybdenum wire section decreases continuously,resulting in the crack propagation failure of molybdenum wire in mechanical bending slower than tearing failure.(5)The curvature radius of self-developed bending surgical instruments can reach 6 mm,which reduces the stress concentration and increases the average life of molybdenum wires to 97 times,while that of rare earth molybdenum alloy electrodes to 197 times.The bending fracture of molybdenum is mainly caused by the simultaneous propagation and penetration of multi-channel cracks and then tearing failure.Fracture of rare earth molybdenum alloys contains homogeneous fracture with multiple slip steps.