Comprehensive Mechanical Properties And Optimal Design Of Flexible Neural Electrode

As a new direction of the development of neural electrode,flexible neural electrode can alleviate the serious immune response caused by the implantation of traditional silicon-based electrode into brain tissue,enhance the long-term stability and improve the working life of electrode as well.However,flexible electrode often faces problems such as difficulty in implantation and difficulty in reaching the target position during the operation process.The application of biodegradable coating is one of the effective methods to solve these issues.How to optimize the design of the parameters of coating as well as flexible electrode to ensure the flexible electrode to be successfully implanted into the target point,and simultaneously minimize the tissue damage has become an important research direction to improve the performance of the flexible electrode.In this study,the flexible electrode coating and the flexible electrode itself were the main research objects,and a variety of evaluation methods from simulation to experiment were established to achieve the optimal design of coating parameters and electrode parameters.Firstly,the flexible electrode coating was studied by simulation calculation and simulation experiment methods respectively.The simulation calculation method was utilized to quantify the mechanical properties of the electrodes during the whole process of implantation into the brain tissue,and to study the effect of different coating thicknesses on the electrode performance.The results show that the increase of coating thickness will trigger an increase in the critical load,a decrease in the maximum deformation and a decrease in brain tissue’s micromotion damage.The previous section used simulation as a means to establish the evaluation method,and analyzed the coating thickness as an example.Then the effects of coating material and wedge angle on implant injury were studied in the experimental environment of the simulation of electrode implantation in brain tissue.Tissue damage was characterized by the maximum strain of brain tissue phantom and the maximum implantation force.The results show that when the wedge angle of the coating is selected in the range of 30°to 60°,the smaller the angle is,the smaller the implanted damage of brain tissue will be;when the average molecular weight of PEG is selected in the range of 10,000 to 100,000,the smaller the molecular weight is,the smaller the implanted damage of brain tissue will be;when the coating material is PEG10000 and the wedge angle is 30°,flexible electrode has the best mechanical properties during implantation.The first two parts were to study the coating,and finally to optimize the flexible electrode itself.Three major factors of elastic modulus,electrode thickness and wedge angle were selected as the research objects.With a combination of orthogonal experimental design approach and mechanical simulation method,each test group was comprehensively evaluated under the fundamental standard of micromotion damage as well as the auxiliary standard of implanted deformation.The results show when the elastic modulus is 8.5GPa,the electrode thickness is 15μm,and the wedge angle is 45°,the maximum strain of the brain tissue achieves the smallest value,as 5.5627×10^-2;when the elastic modulus of intermediate layer polymer is 5.5GPa and the elastic modulus of two-side layer polymer is 8.5GPa,the micromotion damage caused by the three-layer stacked combined flexible electrode will be further reduced.