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Camilo Diaz-Botia, Ph.D. 2017

Advisor: Prof. Maharbiz

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Camilo received his B.S. in Electrical Engineering from Universidad Nacional de Colombia. He spent over 2 years doing research in microfluidic platforms at the Lawrence Berkeley National Lab and UCSF, working on the development of new technologies for high throughput peptide synthesis and other biochemical assays. He also worked in collaboration with the Joint Center for Artificial Photosynthesis and developed a test-bed for proton permeable membranes and photocatalyzers for the development of materials for solar fuel production. He joined the Bioengineering jPhD program at UC Berkeley/UCSF and has taken his knowledge and experience in microfabrication to work in neural engineering developing technologies for Brain-Machine interfaces.

Silicon Carbide ECoGs for Chronic Implants in Brain-Machine Interfaces [BPN771]
Several technologies have been developed for interfacing with the brain such as microwires, electrode arrays, and
electrocorticography (ECoG) arrays. While each of them has strengths and weaknesses, they all share a common disadvantage of
limited device longevity due to a variety of failure modes; these include scar tissue formation and material failure, among others. A
particularly pronounced problem is the failure of the insulating material at the insulator-conductor interfaces (e.g. recording sites
and insulated conducting traces). Damage to these vital interfaces compromises device performance by altering the impedance
of recording sites, or more deleterious, results in total device failure due to shorting between traces or between a trace and
physiological fluid. To address these material issues, we have focused on the fabrication of silicon carbide (SiC) electrode arrays. As
a surface coating, polycrystalline SiC has been shown to promote negligible immune glial response compared to bare silicon when
implanted in the mouse brain. Additionally, due to its mechanical and chemical stability, SiC serves as stable platform and
excellent diffusion barrier to molecules present in the physiological fluid. Moreover, and of particular interest to the
neuroengineering community, the ability to deposit either insulating or conducting SiC films further enables SiC as a platform
material for robust devices. Leveraging these unique properties, we have developed a fabrication process that integrates
conducting and insulating SiC into 64-channel ECoG arrays. Recording sites 40 um in diameter are made of n- doped SiC while the
insulating layers are either amorphous SiC or undoped polycrystalline SiC. To allow for low impedance interconnects, a metal stack
of titanium/gold/titanium or a titanium/platinum is completely embedded in between layers of SiC. The result is an ECoG array
that, to the physiological fluid, appears simply as a single SiC sheet wherein boundaries between conducting and insulating layers
are seamless. The inner metal layer is well protected by SiC and therefore cannot be reached by molecules present in the
physiological fluid. We believe this basic platform can be extended to a variety of electrophysiological devices, including
penetrating probes of various geometries, and help mitigate the failure modes of the present technologies.


     Last Updated: Wed 2018-Mar-14 16:07:06

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