Technology
PGC has developed a proprietary process for co-deposition of platinum and iridium creating a high performance material we call the Electrodeposited Platinum-Iridium Coated (EP-IC) Electrode.
EP-IC electrodes exhibit superior electrical conductivity, superior mechanical robustness, and compositions similar to those used in exisiting biomedical applications.
EP-IC on Non-Planar Surfaces.
EP-IC can be coated easily on virtually any electrode design, including non-planar surface and surfaces which may be difficult to coat using other processes.
DBS style electrode lead consisting of 6 cylindrical platinum electrode contacts, with the first one (dark color) coated with EP-IC around its entire circumference. PGC can provide regularly coated surfaces around 360-degrees of arc on devices like this.
EP-IC PtIr Composition.
EP-IC coating composition ranges between 80-20 PtIr and 60-40 PtIr as validated by XRD (below left) and XPS (below right) analyses. These compositions have been most commonly used in neuromodulation research applications.
EP-IC Electrochemical Properties.
EP-IC electrodes have produced charge densities > 9mC/cm2 in phosphate buffered saline*. Impedance |Z| advantages range from 1 to 1,000 kOhm depending on the coating preparation and frequencies of interest**. The sustainability of these improvements have been demonstrated following 10 years accelerated pulse testing in vitro, and after 180-days in vivo.
Comparison of biphasic potential response of EP-IC (Pt-Ir) coated 200um microelectrode vs. an identical, uncoated Pt microelectrode. The high charge injection capacity of the Pt-Ir in the EP-IC coating causes significant reduction in electrode polarization during biphasic pulsing. [Conditions: 120uA, 1ms pulses in PBS solution]
Normalized impedance spectroscopy plot for a single micro-electrode before (circles) and after EP-IC coating (squares). The result is a reduction of impedance by about three orders of magnitude along frequencies of most concern to neuroscience applications.
Comparison of cyclic voltammagrams of a platinum electrode pre- (horizontal line) and post- EP-IC coating (larger curve). Average currents are more than 100x greater than conventional Pt metal.
EP-IC Mechanical Robustness.
EP-IC exhibits strong cohesion (PtIr grain to PtIr grain) and adhesion (PtIr grain to substrate).
Impedance spectra of EP-IC coated shank electrode inserted into cerebral cortex tissue 30 times, showing virtually no change in impedance following insertion. Whole tissue compositional analysis detected less than 8ppm PtIr (cumulative) in the total tissue block.
EP-IC Efficiency of Deposition.
Our proprietary process does not involve high-vacuum, thin film processing, thus eliminating waste associated with photolithography and masking, and improving processing time by eliminating pump-down/up cycles.
References
EP-IC coating on electrodes for the Rogers Group featured in Advanced Materials.
http://rogers.matse.illinois.edu/files/2015/defibadvmater.pdf
USC Viterbi engineering press release
http://viterbi.usc.edu/news/news/2012/platinum-group-raises.htm
Surface modification of neural stimulating/recording electrodes with high surface area platinum-iridium alloy coatings
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6090823
Improved Biphasic Pulsing Power Efficiency with Pt-Ir Coated Microelectrodes
http://dx.doi.org/10.1557/opl.2014.267