Flexible deep brain neural probe for localized stimulation and detection with metal guide

In this paper, we present the design, fabrication, and performance evaluation of a polyimide-based flexible neural probe for the precise site stimulation and recording in the deep brain. The probe consists of five electrodes: one for stimulation, another for ground and the other three for recording electrodes. This probe is designed to be foldable, enabling easy insertion into the deep brain via temporary tungsten guide sticks. Because of its small cross-sectional area and the flexibility of the polyimide, the probe causes minimum damage to the neural tissue and does not show any evidence of serious immune reactions such as high density of macrophage or microglia. Around the simulation electrodes, an additional ground electrode prevents the stimulation of the undesired sites in the brain. To ensure we stimulate the target point specifically, for instance STh in this study, we confirm through both finite element analyses and in vitro tests. With the additional ground electrodes, we observe the leakage power decreased by about 80%. To check the performance of the probe, we demonstrate animal experiments using rats, and neural spike signals from STh in the 7-mm deep brain are successfully recorded after implantation.