Intracortical Neural Probes with Post-Implant Self-Deployed Electrodes for Improved Chronic Stability.

neural probes;starch;Parylene;microfabrication;electrodes;actuator;Biomedical Engineering;Electrical Engineering;Materials Science and Engineering;Neurosciences;Engineering;Health Sciences;Electrical Engineering

Egert, Daniel G. D.Wise, Kensall D. ;

University of Michigan

关键词: neural probes;    starch;    Parylene;    microfabrication;    electrodes;    actuator;    Biomedical Engineering;    Electrical Engineering;    Materials Science and Engineering;    Neurosciences;    Engineering;    Health Sciences;    Electrical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/113317/egertd_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

This thesis presents a new class of implantable intracortical neural probe with small recording electrodes that deploy away from a larger main shank after insertion. This concept is hypothesized to enhance the performance of the electrodes in chronic applications.Today, electrodes that can be implanted into the brain for months or years, are an irreplaceable tool for brain machine interfaces and neuroscience studies. However, these chronically implanted neural probes suffer from continuous loss of signal quality, limiting their utility. Histological studies found a sheath of scar tissue with decreased neural density forming around probe shanks as part of an ongoing chronic inflammation. This was hypothesized to contribute to the deterioration of recorded signals. The neural probes developed in this thesis are designed to deploy electrodes outside this sheath such that they interface with healthier neurons. To achieve this, an actuation mechanism based on starch-hydrogel coated microsprings was integrated into the shank of neural probes. Recording electrodes were positioned at the tip of micrometer fine and flexible needles that were attached to the springs. Before insertion, the hydrogel dehydrates, retracting the springs. After insertion, the gel rehydrates, releasing the springs, which then deploy the electrodes. The actuation mechanism functions in a one-time release fashion, triggered by contact with biological fluids at body temperature. The deployment of the electrodes occurred over the course of two hours and can be divided into three stages: For the first 20 s, the electrodes did not deploy. Within the first three minutes they deployed by roughly 100 µm (0.5 µm/s). Tor the following two hours they deployed an additional 20 µm (0.17 µm/min). The employed design supported six deploying electrodes, each at the end of a 5 µm wide and thick, and 100 µm long needle. These were attached to a shank with 290 µm width, 12 µm thickness and 3 mm length. The shanks could be inserted into the cortex of rats through an opening in the pia without breaking. The acquired waveforms indicate that some of the deployed electrodes were able to record neural action potentials.