Hydrogel-actuated carbon fiber neural probe

Passivation of neural probe electrodes due to glial scarring is thought to limit the longevity of chronic implants. We present proof of concept for a neural probe insertion method designed to minimize gliosis near the targeted recording site. This method provides passive water-triggered actuation to individual carbon fibers via expansion of a hydrogel. To avoid physical interconnection, the probe is actuated through a micron-scale aperture with a very high leakage resistance to the extracellular fluid; this allows for electrical recordings without direct electrical contact to the fiber. This method is designed to deliver recording electrodes beyond the region of scar tissue formation as well as decrease adverse biological reactions at the electrode. The mechanical utility of the device is demonstrated by penetrating agarose, and the effective electrode impedance is characterized. This technique can provide a platform to improve the lifetime of high-density neural implants.