Study On Flexible Surgical Electrode

With the continuous development of surgical techniques,as well as the increasing requirements of operation safety and wound minimally invasive,minimally invasive surgical instruments are increasingly popular in clinical practice.Since traditional surgical instruments are predominantly oriented with straight or pre-flexible surgical electrodes,it is difficult for a doctor to perform surgical operations in a safe and convenient way in the specific small space,and it also easily lead to unnecessary tissue damage in patients.Traditional surgical instruments are increasingly unable to adapt to the development of minimally invasive medicine.Minimally invasive surgery now requires the device with better flexibility and controllable bending,and the ability to conduct a series of multi-degree of freedom activities in the clinical operation such as stretching,bending,rotation.Therefore,the basic research related to the flexible electrode can be carried out in order to better understand the bending forming performance of the electrode,the heat treatment process of the elastic element,the cutting performance of the electrode,etc..It provides reference for the structural design and performance optimization of the flexible electrode,and important guiding significance on the clinical operation.In this thesis,the molybdenum electrode was repeatedly bent under different conditions to analyze the change of the hammer angle and the microstructure of the molybdenum electrode,and study the effect of stress-strain characteristics at high temperature and bending conditions on the molding behavior of molybdenum material.The Ni36CrTiAl alloy elastic elements were aged at different temperature and holding time,and the effects of aging treatment on the microstructure and mechanical properties of Ni36CrTiAl alloy were studied by metallographic microscope,scanning electron microscope,universal testing machine and Vicker-hardness tester.The effects of the cutting characteristics and the adhesion behavior of the molybdenum electrode and stainless steel electrode under the same conditions for cutting different organizations and burning test were investigated by optical microscopy and Fourier transform infrared spectroscopy.The main conclusions include the following points:?1?Under the same bending forming conditions,45°repeated bending of molybdenum electrodes can be carried out about 20 times,and the rebound angle was8-10°,while 90°bending can only be carried out less than 8 times and the rebound angle was 12-14°.The inner and outer hardness of the bending part of the molybdenum electrode were repeatedly increased,and the hardness of the neutral layer was almost constant.The inside of the bending parts of molybdenum electrode produced cracks before the outside which were perpendicular to the axial direction and extended to a certain depth along the 45°direction.As the number of bending times increased,the number and the depth of cracks increased.Under the heating conditions,the cracks at the bending part of molybdenum electrode were reduced.When bending 90°4 times at 250°C,the cracks disappeared completely.When bending 90°8 times,the plastic forming ability of the molybdenum electrode increased when temperature raised,and the degree of internal cracks was significantly reduced while the lateral cracks changed smaller.?2?Ni36CrTiAl alloy shrapnel was homogeneous austenite before aging treatment,and part of the grain had twins,dislocations and other defects.The mechanical properties were poor,of which the tensile strength was only 898.4MPa,and the yield strength was401.0MPa.Under the same conditions of holding time,the number of secondary phase precipitates in the alloy gradually increased with the increase of the aging treatment temperature,and the second phase particle component was mainly?Ti,Al?₂Ni.The enhancement effect increased first and then decreased when the temperature increased,which achieved the best at 710°C when the tensile strength reached 1459.9MPa and the yield strength reached 967.7MPa which respectively enhanced nearly 62.49%and 1.5times compared to the alloy without aging treatment.When the aging treatment was carried out at 710°C for different holding times,the mechanical properties of the alloy achieved the best at 3h of holding time.?3?Under the same cutting conditions,the area and degree of thermal damage caused by molybdenum electrode were smaller,the wound was narrower,and the surface adhesion of molybdenum electrode was less,compared to that of stainless steel.Cutting different body tissues,the electrode surface appeard different adhesives.When cutting adipose tissue,the electrode surface adhesion was mainly grease and a small amount of yellow scab;When cutting the skin tissue,the electrode surface adhesion was mainly black eschar and a small amount of yellow eschar;When the muscle tissue was cut,the electrode surface adhesion was composed of yellow eschar and flocculent muscle tissue;cutting fat-muscle mixed tissue,the electrode surface adhesion was a mixture of fat and muscle tissue adhesion.Under the high-power discharge test,the molybdenum electrode remained intact needle-like structure,while the surface of the stainless steel electrode was melted,the surface of the electrode was roughened,indicating that the stainless steel electrode had poor burn resistance.When molybdenum electrode was cut at different power,it was too small to cut the organization below 18w,and would cause large tissue damage more than 26w.With the electric knife power increased,the electrode surface adhesion decreased.