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Freeze Drying Improves the Shelf-Life of Conductive Polymer Modified Neural Electrodes

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Blackrock Microsystems, 630 Komas Dr #200, Salt Lake City, UT 84108, USA
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System of Systems Analytics, 11250 Waples Mill Road, Fairfax, VA 22030, USA
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Department of Bioengineering, Volgenau School of Engineering, George Mason University, 4400 University Drive, MS 1G5, Fairfax, VA 22030, USA
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Author to whom correspondence should be addressed.
Academic Editor: Anthony Guiseppi-Elie
Bioengineering 2015, 2(3), 176-183; https://doi.org/10.3390/bioengineering2030176
Received: 29 June 2015 / Accepted: 4 August 2015 / Published: 7 August 2015
Coating microelectrodes with conductive polymer is widely recognized to decrease impedance and improve performance of implantable neural devices during recording and stimulation. A concern for wide-spread use of this approach is shelf-life, i.e., the electrochemical stability of the coated microelectrodes prior to use. In this work, we investigated the possibility of using the freeze-drying process in order to retain the native low impedance state and, thereby, improve the shelf-life of conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT)-PSS modified neural electrodes. Control PEDOT-PSS coated microelectrodes demonstrated a significant increase in impedance at 1 kHz after 41–50 days of room temperature storage. Based on equivalent circuit modeling derived from electrochemical impedance spectroscopy, this increase in impedance could be largely attributed to a decrease in the interfacial capacitance consistent with a collapse and closing of the porous structure of the polymeric coating. Time-dependent electrochemical impedance measurements revealed higher stability of the freeze-dried coated microelectrodes compared to the controls, such that impedance values after 41–50 days appeared to be indistinguishable from the initial levels. This suggests that freeze drying PEDOT-PSS coated microelectrodes correlates with enhanced electrochemical stability during shelf storage. View Full-Text
Keywords: conductive polymer; PEDOT; microwires; impedance; neural electrode conductive polymer; PEDOT; microwires; impedance; neural electrode
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Mandal, H.S.; Cliff, R.O.; Pancrazio, J.J. Freeze Drying Improves the Shelf-Life of Conductive Polymer Modified Neural Electrodes. Bioengineering 2015, 2, 176-183.

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