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Neural probe insertion methods have a direct impact on the longevity of the device in the brain. Initial tissue and
vascular damage caused by the probe entering the brain triggers a chronic tissue response that is known to attenuate
neural recordings and ultimately encapsulate the probes. Smaller devices have been found to evoke reduced
inflammatory response. One way to record from undamaged neural networks may be to position the electrode sites away
from the probe. To investigate this approach, we are developing probes with controllably movable electrode projections,
which would move outside of the zone that is damaged by the insertion of the larger probe. The objective of this study
was to test the capability of conjugated polymer bilayer actuators to actuate neural electrode projections from a probe
shank into a transparent brain phantom.
Parylene neural probe devices, having five electrode projections with actuating segments and with varying widths (50 -
250 μm) and lengths (200 - 1000 μm) were fabricated. The electroactive polymer polypyrrole (PPy) was used to bend
or flatten the projections. The devices were inserted into the brain phantom using an electronic microdrive while
simultaneously activating the actuators. Deflections were quantified based on video images.
The electrode projections were successfully controlled to either remain flat or to actuate out-of-plane and into the brain
phantom during insertion. The projection width had a significant effect on their ability to deflect within the phantom,
with thinner probes deflecting but not the wider ones. Thus, small integrated conjugated polymer actuators may enable
multiple neuro-experiments and applications not possible before.
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