Potential-Biased, Asymmetric Waveforms for Charge-Injection With Activated Iridium Oxide (AIROF) Neural Stimulation Electrodes

Cogan, Stuart F.; Troyk, Philip R.; Ehrlich, J.; Plante, Timothy D.; Detlefsen, D.E.

doi:10.1109/tbme.2005.862572

Cited by 131 publications

(119 citation statements)

References 23 publications

Supporting

Mentioning

115

Contrasting

Order By: Relevance

“…6,10,30,33 Reported Coulombic charges for the capacitance of Ir oxide can further vary between 1 and several hundred mC cm Ir −2 based on the experiment type (faradaic or capacitive), medium, and deposition technique. [34][35][36][37][38] The mass-based capacitances found in this study on Ir oxide are comparable to those previously found in RDE half-cells and single-cell electrolyzers. 6,30 Capacitance has also been used to determine the ECA of Ir nanoparticles and baseline its activity in OER.…”

Section: Resultssupporting

confidence: 87%

Mercury Underpotential Deposition to Determine Iridium and Iridium Oxide Electrochemical Surface Areas

Alia

Hurst

Kocha

et al. 2016

J. Electrochem. Soc.

125

View full text Add to dashboard Cite

Determining the surface areas of electrocatalysts is critical for separating the key properties of area-specific activity and electrochemical surface area from mass activity. Hydrogen underpotential deposition and carbon monoxide oxidation are typically used to evaluate iridium (Ir) surface areas, but are ineffective on oxides and can be sensitive to surface oxides formed on Ir metals. Mercury underpotential deposition is presented in this study as an alternative, able to produce reasonable surface areas on Ir and Ir oxide nanoparticles, and able to produce similar surface areas prior to and following characterization in oxygen evolution. Reliable electrochemical surface areas allow for comparative studies of different catalyst types and the characterization of advanced oxygen evolution catalysts. They also enable the study of catalyst degradation in durability testing, both areas of increasing importance within electrolysis and electrocatalysis.

show abstract

Section: Resultssupporting

confidence: 87%

Mercury Underpotential Deposition to Determine Iridium and Iridium Oxide Electrochemical Surface Areas

Alia

Hurst

Kocha

et al. 2016

J. Electrochem. Soc.

125

View full text Add to dashboard Cite

show abstract

“…This stimulation current corresponds to 10 nC injected per pulse and a maximum electrode charge density of 0.8 mC/cm 2 . Since this charge density exceeds the safe limit for platinum electrodes (0.4 mC/cm 2 [18,19]) we use activated iridium oxide film (AIROF) electrodes, which have a safe charge-injection limit of 1-9 mC/cm 2 [20].…”

Section: System Designmentioning

confidence: 99%

Progress towards a high-resolution retinal prosthesis

et al. 2007

View full text Add to dashboard Cite

Electronic retinal prostheses represent a potentially effective approach for restoring some degree of sight in blind patients with retinal degeneration. Functional restoration of sight would require hundreds to thousands of electrodes effectively stimulating remaining neurons in the retina. We present a design of an optoelectronic retinal prosthetic system having 3mm diameter retinal implant with pixel sizes down to 25 micrometers, which allows for natural eye scanning for observing a large field of view, as well as spatial and temporal processing of the visual scene to optimize the patient experience. Information from a head mounted video camera is processed in a portable computer and delivered to the implanted photodiode array by projection from the LCD goggles using pulsed IR (810 nm) light. Each photodiode converts pulsed light (0.5 ms in duration) into electric current with efficiency of 0.3 A/W using common biphasic power line. Power is provided by the inductively-coupled RF link from the coil on the goggles into a miniature power supply implanted between the sclera and the conjuctiva, and connected to subretinal implant with a thin 2-wire trans-scleral cable.3-dimensional structures in the subretinal prosthesis induce retinal migration and thus ensure close proximity between stimulating electrodes and the target retinal neurons. Subretinal implantations of the 3-dimentional pillar and chamber arrays in RCS rats with 2 and 6 week follow-up demonstrate achievement of intimate proximity between the stimulation cites and the inner nuclear layer. In some instances formation of a fibrotic seal has been observed.

show abstract

“…The large size of the electrodes has limited the density of electrodes that can be placed over a given area. The choice of electrode size has been dictated mostly by the potential for damage to the electrode and surrounding tissue posed by high charge densities [6,7]. Perceptual threshold measurements obtained in blind humans have varied widely, although 0.5 μC/phase is reasonably good representation of the collective results [8].…”

Section: Introductionmentioning

confidence: 99%

Tissue engineering applied to the retinal prosthesis: Neurotrophin-eluting polymeric hydrogel coatings

Winter

Gokhale

Jensen

et al. 2008

Materials Science and Engineering: C

View full text Add to dashboard Cite

Several groups are developing visual prostheses to aid patients with vision loss. While these devices have shown some success in the clinic, they are severely limited by poor resolution, and in many cases have as few as 15 electrodes. Pixel density is poor because high stimulation thresholds require large electrodes to minimize charge density that would otherwise damage the electrode and tissue. A significant contributor to high stimulation threshold requirements is poor biocompatibility. We investigated the application of one system popular in tissue engineering, drug-releasing hydrogels, as a mechanism to improve the tissue-electrode interface. Hydrogels studied (i.e., PEGPLA photocrosslinkable polymers) released neurotrophic factors (i.e., BDNF) known to promote neuron survival and neurite extension in the retina. Hydrogels were examined in co-culture with retinal explants for 7 and 14 days, at which time neurite extension and neurite density was measured. Neurite extension was enhanced in samples exposed to BDNF-releasing hydrogels at 7 days; however, these increases were absent by day 14 suggesting declining drug release. Thus, PEGPLA hydrogels are excellent candidates for short-term (< 14 day) acute release of therapeutic factors in the retina, but will require additional modifications for application with neural prostheses. Additionally, these results suggest that the effects of neurotrophic factors are short-lived in the absence of additional support cues, and tissue engineering systems employing such factors may only produce transient benefits to the patient.

show abstract

Potential-Biased, Asymmetric Waveforms for Charge-Injection With Activated Iridium Oxide (AIROF) Neural Stimulation Electrodes

Cited by 131 publications

References 23 publications

Mercury Underpotential Deposition to Determine Iridium and Iridium Oxide Electrochemical Surface Areas

Mercury Underpotential Deposition to Determine Iridium and Iridium Oxide Electrochemical Surface Areas

Progress towards a high-resolution retinal prosthesis

Tissue engineering applied to the retinal prosthesis: Neurotrophin-eluting polymeric hydrogel coatings

Contact Info

Product

Resources

About