Establishment of a Refined Brain Model for Evaluating Implantation Behavior of Neural Electrode and Research of its Simulated behavior

The long-term reliability of the neural electrode is closely related to its implantation behavior. In order to realize the quantitative research of the implantation behavior in a low-cost and accurate way, a refined brain model containing meninges is proposed. First, the expected simulation material was selected through measuring the elastic modulus based on the method of atomic force microscope indentation technique. As a result, the 2% (mass fraction) agarose gel simulated the gray and white matter, the 7 : 1 (volume ratio) polydimethylsiloxane (PDMS) sheet simulated the pia mater, and the polyvinyl chloride (PVC) film simulated the dura mater. Second, based on designing a three-layer structure mold, the brain model was prepared by inverted pouring to realize a flat implantation surface. Finally, the simulation behavior of the brain model was investigated with the rat brain as a reference. For mechanical behavior of implantation, the implantation force experienced two peaks both in the brain model and the rat brain, maximum values of which were 10.17mN and 7.69mN respectively. The larger implantation force in the brain model will increase the strength requirement for the electrode, but reduce the risk of buckling of that in practical application. For humoral dissolution behavior, the dissolution rates of the polyethylene glycol (PEG) coating of the electrode in the brain model and rat brain were 7 000 μm 3 /s and 5 600 μm 3 /s, respectively. The faster dissolution rate in the brain model will cause the larger thickness of the coating design but provide sufficient implantable time in practical application. The establishment of the brain model and the research of its simulated behavior are beneficial to the size design of the electrode substrate and coating, and research of the implantation mechanism, and further increase the functional life of the electrode.