Flexible Nerve Stimulation Electrode With Iridium Oxide Sputtered on Liquid Crystal Polymer

Abstract

Current electrode designs require flexible substrates that absorb little moisture and provide large charge injection capability. Sputtered iridium oxide films have superior charge injection capabilities versus noble metals and can adhere to various substrates. Liquid crystal polymers (LCP) have very little water absorption compared to other flexible substrates. Therefore, the combination of sputtered iridium oxide film on liquid crystal polymer substrate was studied using 50Hz, 100μs duration, 10mA biphasic current waveforms for 700 hours at 67°C in bicarbonate buffer saline. Scanning electron micrograph (SEM) analysis showed no delamination and approximately 1% of electrode material was lost to the bicarbonate buffer. The charge injection limit and the cathodic charge storage capacity within the water window were 4.6 +/− 1.0mC/cm 2 and 31.5 +/− 6.6mC/cm 2 respectively. Additional electrochemical analysis revealed significant charge imbalance attributed to oxygen reduction within the water window. These results, along with the flexible, chemically inert, biocompatible substrate, indicate that sputtered iridium oxide films on liquid crystal polymer could become the method of choice for flexible substrate nerve electrodes.

Penetrating microelectrode arrays with low-impedance sputtered iridium oxide electrode coatings

“…Without oxygen present, the CSC c of the platinum electrode is reduced to 3.4 mC/cm 2 . Oxygen reduction has also been reported on ~2 μm thick SIROF electrodes [9], although it was not observed in the present 20 μm study with 200 nm to 300 nm SIROF. Both the platinum and SIROF CVs are similar in appearance to those observed in previous studies [1], [5].…”

“…An interphase period of 1.1 ms between the end of the cathodal pulse and the onset of the anodic recharge current was employed to facilitate analysis of the voltage transients. The maximum negative potential excursion was determined from the transient waveform as the electrode potential immediately after the end of the cathodal current pulse [1], [9]. In the present study, cathodal pulse widths of 0.2-1.0 ms and interpulse bias levels of 0.08 V to 0.6 V vs. Ag|AgCl were investigated.…”

High‐charge‐capacity sputtered iridium oxide neural stimulation electrodes deposited using water vapor as a reactive plasma constituent

“…Therefore, the electrodes are negatively polarized and oxygen reduction can occur at these potentials (Cogan, Ehrlich, Plante, Gingerich, & Shire, 2010). The products from oxygen reduction are reactive and potentially injurious to tissue (Morton, Daroux, & Mortimer, 1994;Wang, Liu, & Durand, 2009). The contribution of oxygen reduction to charge injection during current pulsing has been discussed previously in terms of the oxygen concentration and diffusion in buffered saline (Cogan et al, 2010).…”

Sensitivity and packaging improvement of an LCP pressure sensor for intracranial pressure measurement via FEM simulation

“…LCP is an appealing material for this application as it is biocompatible, has low moisture absorption and it has a wide range of chemical resistances. Reported applications of LCP in a biological environment include: the use of LCP as a flexible electrode for neural stimulation [8][9][10], as an interconnect for an implanted device [11], and as packaging for an implantable sensor [12]. Given that medical grade LCP sheet is easily available [13], it is an attractive material for the minimally invasive measurement of ICP.…”