Design And Puncture Performance Of Cryogenic Gelatin Coating Electrodes For Deep Brain Stimulation

Aiming at the problem that the puncture friction caused by the interaction between the cannula electrode and the brain tissue causes damage to the brain tissue during deep brain stimulation surgery,this paper combines the surface modification of biomedical metal materials and the idea of extremely low friction coefficient on the ice surface.The surface of 316 L stainless steel material was modified by ice / gelatin coating,and the friction performance of the ice surface was explored.The effects of different texture morphologies on the bonding properties of gelatin coatings were investigated,and the mechanism of textured surface improving the bonding properties of gelatin coatings was revealed.The low temperature gelatin coated electrode was designed and prepared.The anti-friction performance of the low temperature gelatin coated electrode was verified by the puncture test of fresh pig brain tissue.(1)Gelatin coating was prepared on the surface of medical 316 L stainless steel plate by physical coating method,and its surface material modification was completed to improve its biocompatibility.The ice coating was prepared on the surface of the modified medical316 L stainless steel plate by a specific method.In order to explore the friction performance of the ice surface,large-section and large-thickness brain tissue sections were prepared for the friction performance test of the ice surface.The ice surface traction test was carried out on the brain tissue sections in different regions of the puncture path.The results show that the friction force and brain tissue damage on the surface of the smooth stainless steel plate are larger,and the friction force and brain tissue damage on the ice surface are very small.At the same speed,the friction force on the ice surface is reduced by about 50% ～ 80%.Therefore,the ice surface has excellent anti-friction effect.(2)Combining the relationship between surface wettability and coating adhesion and the improvement of surface wettability of different micro-pit texture arrays,the microtexture morphology and size with the best bonding performance of gelatin coating were selected.Four kinds of micro-pit texture arrays with square,circular,regular hexagon and triangle were prepared on the surface of medical 316 L stainless steel plate with a spacing of200 μm and a size of 100 μm ～ 400 μm.Gelatin coating was grafted on the surface of the sample with four kinds of micro-pit texture arrays.The effects of different surface morphologies on the bonding properties of gelatin coating were investigated by gridding method.The results show that the order of bonding properties of gelatin coating is square,circular,hexagonal and triangular.When the square micro-pit texture spacing-size is 200μm-400 μm,the gelatin coating on the surface of the texture array has the smallest shedding,the shedding area ratio is 0.72 %,and the gelatin coating has the best bonding performance.Combined with the wettability experiment of textured surface,the mechanism of laser textured surface improving the adhesion of gelatin coating was explored.The results show that compared with the smooth surface,the four kinds of micro-pit texture arrays can improve the wettability of the surface of medical 316 L stainless steel plate.The order of wettability is square,round,hexagon and triangle.When the square micro-pit texture spacing-size is 200 μm-400 μm,the contact angle of water droplets is the smallest,the wettability is the best,the corresponding contact angle of water droplets is 52.98?,the binding force between liquid and solid does the most work,and the adhesion performance of gelatin coating is the best.The results of the above experiments show that when the square micro-pit texture spacing-size is 200 μm-400 μm,the gelatin coating on the surface of the texture array has the best bonding performance.Therefore,the morphology and size of the micro-pit texture on the surface of the casing electrode to increase the binding force of the gelatin coating are set to be square and 400 μm.(3)Combined with the idea of improving the binding force of gelatin coating by microtexture,the preparation of square micro-pit textured electrode was completed according to the results of grid method experiment and textured surface wettability experiment.The square micro-pit textured electrode was used as the substrate,and the gelatin coating was grafted on the surface by physical coating to realize the modification of the electrode surface material.The preparation of low temperature gelatin coated electrode was completed by grafting ice coating on the surface of gelatin coated square micro-pit texture electrode by a specific method.(4)A single puncture experiment was performed on fresh pig brain tissue using a smooth electrode and a low-temperature gelatin-coated electrode at a puncture speed of 2mm/s,3 mm/s,4 mm/s,and 5 mm/s,respectively.The NANO17 was used to collect the puncture force during the experiment and draw the puncture force curve.The adhesion of brain tissue on the surface of low temperature gelatin coated electrode and its friction growth rate were observed and analyzed.The results show that there is almost no brain tissue adhesion on the surface of the low temperature gelatin coated electrode compared with the smooth electrode,and the friction growth rate of the low temperature gelatin coated electrode shaft surface is reduced by 23.4%～32.8%.Therefore,the low temperature gelatin coated electrode has good antifriction effect.