Electropolymerized Poly(3,4-ethylenedioxythiophene) (PEDOT) Coatings for Implantable Deep-Brain-Stimulating Microelectrodes.

Conducting polymers have been widely explored as coating materials for metal electrodes to improve neural signal recording and stimulation because of their mixed electronic-ionic conduction and biocompatibility. In particular, the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the best candidates for biomedical applications due to its high conductivity and good electrochemical stability. Coating metal electrodes with PEDOT has shown to enhance the electrode's performance by decreasing the impedance and increasing the charge storage capacity. However, PEDOT-coated metal electrodes often have issues with delamination and stability, resulting in decreased device performance and lifetime. In this work, we were able to electropolymerize PEDOT coatings on sharp platinum-iridium recording and stimulating neural electrodes and demonstrated its mechanical and electrochemical stability. Electropolymerization of PEDOT:tetrafluoroborate was carried out in three different solvents: propylene carbonate, acetonitrile, and water. The stability of the coatings was assessed via ultrasonication, phosphate buffer solution soaking test, autoclave sterilization, and electrical pulsing. Coatings prepared with propylene carbonate or acetonitrile possessed excellent electrochemical stability and survived autoclave sterilization, prolonged soaking, and electrical stimulation without major changes in electrochemical properties. Stimulating microelectrodes were implanted in rats and stimulated daily, for 7 and 15 days. The electrochemical properties monitored in vivo demonstrated that the stimulation procedure for both coated and uncoated electrodes decreased the impedance.

Poly(3,4-ethylenedioxythiophene) (PEDOT) Coatings for High-Quality Electromyography Recording.

Conducting polymer coatings on metal electrodes are an efficient solution to improve neural signal recording and stimulation, due to their mixed electronic-ionic conduction and biocompatibility. To date, only a few studies have been reported on conducting polymer coatings on metallic wire electrodes for muscle signal recording. Chronic muscle signal recording of freely moving animals can be challenging to acquire with coated electrodes, due to muscle movement around the electrode that can increase instances of coating delamination and device failure. The poor adhesion of conducting polymers to some inorganic substrates and the possible degradation of their electrochemical properties after harsh treatments, such as sterilization, or during implantation limits their use for biomedical applications. Here, we demonstrate the mechanical and electrochemical stability of the conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT) doped with LiClO4, deposited on stainless steel multistranded wire electrodes for invasive muscle signal recording in mice. The mechanical and electrochemical stability was achieved by tuning the electropolymerization conditions. PEDOT-coated and bare stainless steel electrodes were implanted in the neck muscle of five mice for electromyographic (EMG) activity recording over a period of 6 weeks. The PEDOT coating improved the electrochemical properties of the stainless steel electrodes, lowering the impedance, resulting in an enhanced signal-to-noise ratio during in vivo EMG recording compared to bare electrodes.