Cabon Fiber Devices

Developing novel biomaterials to interfaces with neural activity. Implantable neural interface devices are a critical component to a broad class of emerging neuroprosthetic and neurostimulation systems, in both research and clinical settings. In almost all cases, the performance of the system hinges to a large degree on the performance of the device to record and/or stimulate within quality, stability, and longevity requirements. Recording quality, longevity and stability is highly variable according to numerous reports, and the reactive tissue response that occurs to devices following implantation is a likely key contributing factor. The fundamental challenge is to develop advanced materials and implantable structures that will enable neural interface devices to be implanted in target areas of the brain and remain functional for as long as needed, sometimes stretching into years and decades. This project aims to develop and evaluate innovative strategies that uses leading-edge biocompatible polymers to develop innovative 'microthread neural probes' that are ultra-small and flexible, with bioactive surfaces and nanostructured electrode sites for enhanced signal transduction. We will create these microthread probes using advanced carbon nanotube (CNT) and bioactive polymer coating technologies. The primary of this project is to integrate CNT and functionalized polymer coating technologies into microthread neural probes that can be reliably inserted into the brain and used for chronic recording, chronic electrical stimulation, chronic wireless stimulation, chronic chemical sensing, and chronic wireless drug delivery. The design space includes size, flexibility, strength, conductivity, site electrical characteristics, insulating coating, insertion techniques, and electrode size. This project is likely to make significant contributions through developing advanced neural probes for long-term (permanent), high quality neural interfaces.

The outcomes of this project are also likely to establish new biologically inspired paradigms for creating long-lasting, high-fidelity neural interfaces with biomimetic materials. This project will impact both the neuroscience research community, and clinical communities (neurosurgeons, neurologists, and patients) that use and benefit from neuroprosthetic- and neurostimulation-based treatments interventions. The public health relevance of this project is to improve neural prosthetic and neural stimulation devices for treatment of neurological diseases or injury.

When the opportunity arises, we capitalize on opportunistic engineering. By understanding the fundamental science behind brain injury and downstream consequences to neuronal activity, it becomes abundantly clear which of the competing design parameters need to be prioritized1. It is this philosophy that led to the design of the chronically implantable carbon fiber ultra-microelectrodes, which was ultimately published in Nature Materials2. Similarly, we discovered that it was much more difficult to eliminate the two-photon photoelectric effect on carbon fiber electrodes during simultaneous electrophysiology and two-photon imaging experiments, which we discussed in detail in the Journal of Material Chemistry B3. We instead used this “bug” as a “feature” to drive wireless electrical stimulation in free-floating carbon fiber electrodes in the brain, which was recently published in IEEE TBME4. While it is difficult to predict when basic science research exposes opportunities for innovative engineering, we demonstrate that we have the capability to capitalize on these opportunities.

Our research program is taking a more "long-ranged view" in building fundamental knowledge and filling in basic science gaps. By understanding and uncovering the underlying scientific principles, we build foundational knowledge that can more readily apply to new conditions.

1 Wellman, S. M. et al. A Materials Roadmap to Functional Neural Interface Design. Advanced Functional Materials 28, 201701269, doi:10.1002/adfm.201701269 (2018).

2 Kozai, T. D. Y. et al. Ultrasmall implantable composite microelectrodes with bioactive surfaces for chronic neural interfaces. Nat Mater 11, 1065-1073, doi:10.1038/nmat3468 (2012).

3 Kozai, T. D. Y. & Vazquez, A. L. Photoelectric artefact from optogenetics and imaging on microelectrodes and bioelectronics: New Challenges and Opportunities. Journal of Materials Chemistry B 3, 4965-4978 (2015).

4 Stocking, K. C., Vazquez, A. L. & Kozai, T. D. Y. Intracortical neural stimulation with untethered, ultrasmall carbon fiber electrodes mediated by the photoelectric effect. Ieee T Bio-Med Eng (2019).