SiC protective coating for photovoltaic retinal prosthesis

Lei, Xin; Kane, Sheryl R.; Cogan, Stuart F.; Lorach, Henri; Galambos, Ludwig; Huie, Philip; Mathieson, Keith; Kamins, Theodore I.; Harris, James S.; Palanker, Daniel

doi:10.1088/1741-2560/13/4/046016

Cited by 55 publications

(44 citation statements)

References 64 publications

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“…Our group believes an alternative material strategy may address both issues simultaneously. The device would be constructed exclusively of one material which has a demonstrated track record of physical robustness, chemical inertness, and a great degree of biological tolerance: crystalline silicon carbide (SiC) [ 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. Additionally, the amorphous form of SiC ( a -SiC) has also been demonstrated as an effective insulating coating which does not take up water and is very compatible with neural cells [ 25 , 32 , 33 ].…”

Section: Introductionmentioning

confidence: 99%

Demonstration of a Robust All-Silicon-Carbide Intracortical Neural Interface

Bernardin

Frewin²,

Everly³

et al. 2018

Micromachines

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Intracortical neural interfaces (INI) have made impressive progress in recent years but still display questionable long-term reliability. Here, we report on the development and characterization of highly resilient monolithic silicon carbide (SiC) neural devices. SiC is a physically robust, biocompatible, and chemically inert semiconductor. The device support was micromachined from p-type SiC with conductors created from n-type SiC, simultaneously providing electrical isolation through the resulting p-n junction. Electrodes possessed geometric surface area (GSA) varying from 496 to 500 K μm2. Electrical characterization showed high-performance p-n diode behavior, with typical turn-on voltages of ~2.3 V and reverse bias leakage below 1 nArms. Current leakage between adjacent electrodes was ~7.5 nArms over a voltage range of −50 V to 50 V. The devices interacted electrochemically with a purely capacitive relationship at frequencies less than 10 kHz. Electrode impedance ranged from 675 ± 130 kΩ (GSA = 496 µm2) to 46.5 ± 4.80 kΩ (GSA = 500 K µm2). Since the all-SiC devices rely on the integration of only robust and highly compatible SiC material, they offer a promising solution to probe delamination and biological rejection associated with the use of multiple materials used in many current INI devices.

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Section: Introductionmentioning

confidence: 99%

Demonstration of a Robust All-Silicon-Carbide Intracortical Neural Interface

Bernardin

Frewin²,

Everly³

et al. 2018

Micromachines

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“…To convert the pupil location in pixel coordinates to angular orientation of the eye relative to the orbit, we used the model in Equation 3. The six free variables were found by minimizing the spread (i.e.…”

Section: Discussionmentioning

confidence: 99%

“…However, this requires both sensor miniaturization and assuring the sensor's survival in the eye's hostile environment. Coating the sensors to withstand the vitreous environment showed promising results in the lab, 3 but has not yet been tested in humans. One straightforward solution is to use an external sensor and to only implant the stimulation unit in the eye.…”

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confidence: 99%

Retinotopic to Spatiotopic Mapping in Blind Patients Implanted With the Argus II Retinal Prosthesis

Caspi

Roy

Dorn

et al. 2017

Invest. Ophthalmol. Vis. Sci.

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Citation: Caspi A, Roy A, Dorn JD, Greenberg RJ. Retinotopic to spatiotopic mapping in blind patients implanted with the Argus II retinal prosthesis. Invest Ophthalmol Vis Sci. 2017;58:119-127. DOI:10.1167/ iovs.16-20398 PURPOSE. To quantify the precision of mapping from retinotopic (retina-centered) to spatiotopic (world-centered) coordinates in blind humans implanted with a retinal prosthesis device. Additionally, to demonstrate that an eye tracker can be calibrated on sightless patients based on the percept from a visual implant. METHODS.We directly activated epiretinal electrodes to create retinotopic stimuli and recorded the location of the percept at world-based coordinates. In contrast to normal Argus II use where stimulation is a function of the captured scene's image, in this research we directly controlled the waveform in each electrode and measured the percept's location using a trackable handheld marker. For eye tracking, pupil images were recorded with a timestamp synchronized to the stimulation and marker positions. RESULTS.Remapping of the measured world locations to the position of the electrodes on the retina is feasible by accounting for eye orientation at the onset of stimulation. Transformation of pupil images to the eye's orientation (i.e., eye tracker calibration) can be done by solving for the variables that minimize the spread of the remapped retinal electrode locations. After mapping to retinal coordinates based on eye positions, the measured precision of pointing was 28 to 38, which is comparable to open-loop pointing in sighted individuals.CONCLUSIONS. The brain accurately maps the artificial vision induced by a retinal prosthesis based on instantaneous gaze position. Remapping based on eye position is feasible and will increase visual stability in prosthetic vision.

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“…Alternatively, amorphous silicon carbide (a-SiC) has emerged as a candidate encapsulation material for next generation brain implants (68)(69)(70)(71). Created through plasma enhanced chemical vapor deposition, a-SiC films exhibit robust long-term stability, high electronic resistivity, and resistance to corrosion (68,72,73).…”

Section: Future Opportunities For Reproducible and Scalable Fabricatimentioning

confidence: 99%

Thinking Small: Progress on Microscale Neurostimulation Technology

Pancrazio

Deku

Ghazavi

et al. 2017

Neuromodulation: Technology at the Neural Interface

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Objectives Neural stimulation is well-accepted as an effective therapy for a wide range of neurological disorders. While the scale of clinical devices is relatively large, translational and pilot clinical applications are underway for microelectrode-based systems. Microelectrodes have the advantage of stimulating a relatively small tissue volume which may improve selectivity of therapeutic stimuli. Current microelectrode technology is associated with chronic tissue response which limits utility of these devices for neural recording and stimulation. One approach for addressing the tissue response problem may be to reduce physical dimensions of the device. “Thinking small” is a trend for the electronics industry, and for implantable neural interfaces, the result may be a device that can evade the foreign body response. Materials and Methods This review paper surveys our current understanding pertaining to the relationship between implant size and tissue response and the state-of-the-art in ultra-small microelectrodes. A comprehensive literature search was performed using PubMed, Web of Science (Clarivate Analytics), and Google Scholar. Results The literature review shows recent efforts to create microelectrodes that are extremely thin appear to reduce or even eliminate the chronic tissue response. With high charge capacity coatings, ultra-microelectrodes fabricated from emerging polymers and amorphous silicon carbide appear promising for neurostimulation applications. Conclusion We envision the emergence of robust and manufacturable ultra-microelectrodes that leverage advanced materials where the small cross-sectional geometry enables compliance within tissue. Nevertheless, future testing under in vivo conditions is particularly important for assessing the stability of thin film devices under chronic stimulation.

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SiC protective coating for photovoltaic retinal prosthesis

Cited by 55 publications

References 64 publications

Demonstration of a Robust All-Silicon-Carbide Intracortical Neural Interface

Demonstration of a Robust All-Silicon-Carbide Intracortical Neural Interface

Retinotopic to Spatiotopic Mapping in Blind Patients Implanted With the Argus II Retinal Prosthesis

Thinking Small: Progress on Microscale Neurostimulation Technology

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