Design and Fabrication of MRI-Compatible and Flexible Neural Microprobes for Deep Brain Stimulation and Neurological Treatment Applications

Abstract This paper presents a new design and fabrication method of flexible neural microprobes for deep brain stimulations (DBS) and neurological treatment applications. The developed new flexible microprobes are compatible with functional magnetic resonance imaging (fMRI) and can be used for neurological studies of brain functions under functional imaging such as fMRI for a long period of time. In this paper, the materials of the flexible neural microprobes are comprehensively selected to minimize the magnetic resonance imaging (MRI) artifacts, which limits many conventional feasible manufacturing processes to be used. Polyimide was adopted for the substrate of the neural microprobe, which has good biocompatibility and a relatively lower Young’s modulus. A 200 nm chromium reinforcement layer was embedded in the microprobe to attenuate its implantation stiffness while remaining flexible. Gold electroplating was employed to modify the electrode sites to improve the signal quality and sensitivity. The designed new neural microprobes were successfully fabricated at our NCSU Nanofabrication Facility (NNF) and bonded to a customized PCB. After the fabrication, the developed neural microprobes were characterized to validate their effectiveness. In vivo simultaneous DBS-fMRI experiments were conducted in surgery rooms on a rat’s deep brain targets, demonstrating the potential applications of our neural microprobe for neuroscience studies, medical diagnosis, and treatment applications. In vivo electrophysiology results show the effectiveness of our fabricated neural microprobes.