Biomedical Sensors and Subsystems

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Silicon and Parylene Intracortical Neural Probes for Chronically-Stable Recording
Daniel Egert, Rebecca L. Peterson, and Khalil Najafi
3-D drawing of silicon probes with integrated springs (left) and Parylene probes with implemented stiffeners and sharp tips (right).
3-D drawing of silicon probes with integrated springs (left) and Parylene probes with implemented stiffeners and sharp tips (right).

Next-generation neuroprostheses assist functional motor control, aid the visually impaired or those suffering loss of hearing. A key feature for the control of neuroprostheses is the ability to record brain activity of awake, freely behaving hosts accurately enough such that action potentials from single neurons can be distinguished. To date only intracortical neural probes can provide that. The high spatial resolution of intracortical neural probes comes at the cost of a high degree of invasiveness; the host immune response often inhibits recording chronically.

This project pursues two technologies for neural probes that allow mitigating the immune response from the host to implanted neural probes and its impact on their performance. The developed neural probes consist of silicon or Parylene formed to millimeter-long needle-like shanks hosting multiple microelectrodes. One technology, based on silicon, supports individual electrodes that are placed at the end of very fine and flexible needle extensions to the shank that are deployed after implantation. The sites act like satellites, floating almost freely inside the brain tissue. These very small satellite electrodes are expected suffer less immune response. A second approach, based on Parylene, addresses a tradeoff between designing a shank large enough to be reliably implanted and the increase in tissue damage with size of the shank. The developed process technologies allow formation of sharp tips and the strategic design of the shank increases its mechanical robustness without significantly increasing its size.

This work is supported by the DARPA Hybrid Insect MEMS program under grant # N66001-07-1-2006.

Updated 04/30/2012