Electrodes Testing and Evaluation Services

EIC Laboratories offers extensive electrochemical evaluation and long-term testing of FES and related electrodes. The process of electrode evaluation usually has three steps:

• Consultation with EIC to establish appropriate tests and protocols to meet the clients objectives.
• Electrode valuation and data reduction.
• Preparation and submission of a comprehensive report.

The electrochemical behavior and stability of electrodes can be evaluated by:

• Cyclic voltammetry
• Potential transient measurements during current pulsing
• Electrochemical impedance spectroscopy
• Many standard potentiodynamic and galvanostatic and dynamic techniques
• Dissolution by ICP-AA analysis of test electrolytes
• Scanning electron microscopy

Electrochemical measurements are made in physiological electrolytes at room temperature, 37°C, or at elevated temperature for accelerated testing. We have the capability to conduct long-term, in vitro testing of electrodes subjected to a variety of electrical and chemical challenges.

Hermetic Coatings

EIC Laboratories uses Plasma Enhanced Chemical Vapor Deposition (PECVD) to coat planar and non-planar substrates with insulting, dielectric films. These films are used as protective coatings for implantable materials and devices. Any combination of the four dielectrics, silicon oxide, silicon nitride, silicon carbide, silicon oxycarbide, can be deposited on metals and plastics at temperatures from 100^oC to 400^oC.

Studies at EIC have shown that the silicon carbide and oxycarbide are more stable in physiologic media than either silicon oxide or silicon nitride. Silicon carbide, which is amorphous with an electronic resistivity of ~1013 W-cm when deposited at < 400^oC by PECVD, has been used on fluoropolymer, polyimide, and metal substrates. The iridium shaft electrode shown in the picture below was insulated with ~1 mm of amorphous SiC. Underlying electrode sites are exposed by grinding or laser ablation.

Polymer coatings based on the silicones and fluoropolymers are also available.

Iridium Oxide Electrodes

Iridium oxide electrodes are used when high charge injection densities or low impedance is required. EIC Laboratories can prepare iridium oxide coatings by:

• Activation of iridium metal by potential cycling (AIROF)
• Electrodeposition of iridium oxide (EIROF)
• Reactive sputtering from iridium metal (SIROF)
• Thermal decomposition of an iridium salt solution (TIROF)

• Consultation to establish the form and properties of iridium oxide most suitable for the clients application.
• Development of protocols for coating the client's electrode.
• Benchmarking in vitro performance.
• Volume coating in support of electrode manufacturing.

EIROF information sheet
Iridium Oxide literature/bibliography

Thin Film Metal Coatings

EIC Laboratories uses sputtering and e-beam evaporation to deposit metal films for electrodes, electrical interconnects and protective coatings. Typical metals and their applications are

Many other metals including silver, molybdenum, ruthenium, nickel and iron are available. EIC has the capability to deposit binary and ternary alloy films of any combination of these metals as well as to deposit films with compositional gradients. Metal films on planar substrates can be photolithographically patterned using lift-off or etch-back techniques.

Metal films are characterized by:

• Electrochemical measurements.
• Profilometry for thickness.
• Scanning electron microscopy for thickness, morphology and composition (X-ray EDS).
• X-ray diffraction.
• Electrical resistivity.
• Hot water immersion, salt spray, and thermal cycling for stability and corrosion resistance.