Scientists have long been trying to understand the workings of the brain by measuring electrical neural activity. The invention of the micro-electrode array (MEA), or neural probe, was a great step improving neuroscientists' capabilities of recording neural activity. Neural probes allow for repeatable and customizable sizing and spacing of electrodes that is out of reach of wire electrodes. This, combined with improvements in recording hardware, on-probe electronics, and action potential detection algorithms, has brought great advancements in the fields of neuroscience and brain-machine interfaces. The original neural probes were fabricated using silicon, due to the technology available at the inception of neural probes. However, many researchers have fabricated neural probes out of various combinations of materials. The most popular materials seem to be silicon-based materials and polymers such as polyimide, SU-8, and Parylene C. One material of particular interest, due to its combination of advantageous chemical and mechanical properties, is polycrystalline diamond. Diamond is a good material for neural probes because it has a high Young's modulus (~1011 Pa), it has good biocompatibility, it is resistant to fouling, and it is chemically inert. The main obstacle to developing diamond-based neural probes is that diamond's beneficial properties also make it difficult to micromachine, making it difficult to develop processes for probe fabrication.One major problem with diamond probe fabrication is that diamond is incompatible with many materials, due to the high temperatures involved in depositing diamond. However, because diamond has a large band gap (~5.5 eV), it is a good candidate for single material MEMS (SMM). SMM devices use only one material for their structural material, insulators, semiconductors, and conductors. This is accomplished by selectively doping the material (diamond) to create different electrical properties for different parts of the structure. By using the SMM process to fabricate neural probes, many of the problems with incompatible materials are resolved. However, SMM fabrication has its own set of issues associated with it.The goal of this work is to develop a process to fabricate single-material diamond neural probes, fabricate the neural probes, and test the neural probes. A process for fabrication of single-material diamond has been presented and details on the fabrication of the probes has been provided. Furthermore, these single-material diamond neural probes have been used for in-vivo electrical neural recordings and in-vitro electrochemical detection. The electrical recordings were also analyzed using a continuous wavelet transform method in order to improve action potential detection. A comparison is also made between silicon-based neural probes, diamond-based neural probes, and single-material-diamond neural probes.This work marks the first time that SMM neural probes have been fabricated and tested, the first time that a functional SMM device was tested, and the first time that a SMM device was used in vivo.
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