Optimal Design Of The Neural Electrode Based On Mechanical Coupling Property

Implantable neural electrode is the key component of brain-computer interface system.Currently,commercial electrodes have been able to successfully collect ECoG signals or perform electrical stimulation,and have been widely applied in clinical practice.However,the application of neural probe is faced with the technical problem of poor long-term stability.Based on previous studies,the electrode will cause acute tissue injury during the insertion process,and the micro-motion of the brain will bring more tissue injury after implantation.The tissue wrap caused by tissue injury is the root cause of electrode failure.Therefore,optimizing the electrode to reduce the tissue injury is one of the main means to increase the service life of electrodes.Based on the mechanical coupling property between the electrode and brain tissue,a novel multi-shank electrode was developed from three aspects: electrode basic parameters,coating selection and structural design.Numerical simulation and experimental results have proved that the novel electrode will significantly reduce tissue injury,which is conductive to increase the long-term lifetime of neural electrodes.Firstly,based on the method of orthogonal design,the influence of five basic parameters of neural electrode(tip fillet,wedge angle,electrode thickness,stiffness and surface friction coefficient)on the micro-motion induced injury of brain tissue was studied.The results show that the tip fillet,wedge angle and thickness of electrode have a very significant impact on the brain tissue damage.Taking into account the interaction between the factors,the optimal parameters of the electrode are the fillet of 20?m,wedge angle of 45°,thickness of 40?m,Young's modulus of 200 GPa,and friction coefficient of 0.1.Based on the optimal electrode parameters obtained above,the insertion injury caused by electrodes coated with biodegradable coatings(silk fibroin,sodium alginate hydrogel and maltose)was evaluated.The experimental results show that compared with the bare electrode,the three coatings can effectively reduce the insertion injury of brain tissue,and maltose is the best choice for neural electrodes coating at the production temperature of 150 °C.Finally,based on the rationality principles of electrode site distribution,a novel multi-shank electrode was developed using the optimal electrode parameters and the optimal coating above.The performance of the novel electrode was evaluated by numerical simulation and experiment respectively.The results show that the multi-shank structure of the novel electrode can effectively reduce the insertion injury and micro-motion induced injury of the brain tissue compared with the reference electrode.And with the increase of implantation time,the advantages of the novel electrode are more obvious,which has important reference value for reducing the tissue injury clinically and is conductive to increase the service life of neural electrodes.