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Most implantable chronic neural probes have fixed electrode sites on the shank of the probe. Neural probe shapes and
insertion methods have been shown to have considerable effects on the resulting chronic reactive tissue response that
encapsulates probes. We are developing probes with controllable articulated electrode projections, which are expected
to provoke less reactive tissue response due to the projections being minimally sized, as well as to permit a degree of
independence from the probe shank allowing the recording sites to "float" within the brain. The objective of this study
was to predict and analyze the force-generating capability of conducting polymer bilayer actuators under physiological
settings.
Custom parylene beams 21 μm thick, 1 cm long, and of varying widths (200 - 1000 μm) were coated with Cr/Au.
Electroplated weights were fabricated at the ends of the beams to apply known forces. Polypyrrole was
potentiostatically polymerized to varying thicknesses onto the Au at 0.5 V in a solution of 0.1 M pyrrole and 0.1 M
dodecylbenzenesulfonate (DBS). Using cyclic voltammetry, the bilayer beams were cycled in artificial cerebrospinal
fluid (aCSF) at 37 °C, as well as in aqueous NaDBS as a control. Digital images and video were analyzed to quantify the
deflections. The images and the cyclic voltammograms showed that divalent cations in the aCSF interfered with
polymer reduction.
By integrating polypyrrole-based conducting polymer actuators, we present a type novel neural probe. We demonstrate
that actuating PPy(DBS) under physiological settings is possible, and that the technique of microfabricating weights onto
the actuators is a useful tool for studying actuation forces.
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