Optimizing photodiode arrays for the use as retinal implants

Schubert, M.B.; Hierzenberger, A.; Lehner, H.J.; Werner, Jürgen

doi:10.1016/s0924-4247(98)00313-6

Cited by 27 publications

(15 citation statements)

References 8 publications

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“…For phase shift lithography, it would be quite difficult to engineer the phase mask to correct for the mechanical deformations, and thus elimination of the distortions would likely require manipulation of the exposure conditions. [22] Advances in microfabrication, namely in the area of nonplanar electronic devices, such as curved photodiode arrays for solar cell applications and synthetic retinal implants, [36][37][38][39][40] demand the ability to pattern metals, and other materials with electrical functionality, on geometrically diverse surfaces. The aforementioned fabrication methods are intended to replace traditional contact lithography by finding novel ways to use PDMS as a patterning element.…”

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confidence: 99%

Fabrication of Flexible Binary Amplitude Masks for Patterning on Highly Curved Surfaces

Bowen

Nuzzo

2009

Adv Funct Materials

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This paper describes soft lithography methods that expand current fabrication capabilities by enabling high‐throughput patterning on nonplanar substrates. These techniques exploit optically dense elastomeric mask elements embedded in a transparent poly(dimethylsiloxane) (PDMS) matrix by vacuum‐assisted microfluidic patterning, UV–ozone‐mediated irreversible sealing, and chemical etching. These protocols provide highly flexible photomasks exhibiting either positive‐ or negative‐image contrasts, which serve as amplitude masks for large‐area photolithographic patterning on a variety of curved (and planar) surfaces. When patterning on cylindrical surfaces, the developed masks do not experience significant pattern distortions. For substrates with 3D curvatures/geometries, however, the PDMS mask must undergo relatively large strains in order to make conformal contact. The new methods described in this report provide planar masks that can be patterned to compliantly compensate for both the displacements and distortions of features that result from stretching the mask to span the 3D geometry. To demonstrate this, a distortion‐corrected grid pattern mask was fabricated and used in conjunction with a homemade inflation device to pattern an electrode mesh on a glass hemisphere with predictable registration and distortion compensation. The showcased mask fabrication processes are compatible with a broad range of substrates, illustrating the potential for development of complex lithographic patterns for a variety of applications in the realm of curved electronics (i.e., synthetic retinal implants and curved LED arrays) and wide field‐of‐view optics.

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confidence: 99%

Fabrication of Flexible Binary Amplitude Masks for Patterning on Highly Curved Surfaces

Bowen

Nuzzo

2009

Adv Funct Materials

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“…10 In 2003, the company Retina Implant was formed from this group. As natural photoreceptors are much more efficient than photodiodes, the group chose to install an additional set of photodiodes that are irradiated by infrared light and generate electrical power to supply the amplification circuits in the retinal implant, 11 before developing an active power source (where the photodiodes are modulating current delivered from an external source) (Figure 1). In 2006, an active hybrid 1500 microphotodiode array (MPDA) was implanted into the subretinal space of six patients for 30 days (although one patient later refused to have it removed).…”

Section: Optoelectronic Approachesmentioning

confidence: 99%

Current and future prospects for optoelectronic retinal prostheses

Dowling

2008

Eye

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There has been accelerating progress in the development of retinal prosthesis systems designed to partially restore vision to people with retinitis pigmentosa or macular degeneration. Current retinal prostheses can be divided into two types: those that receive power and information from passive or active photodiodes (optoelectronic systems) and those based on multielectrode arrays powered by cables or transcutaneous telemetry systems. Currently, four research groups have ongoing chronic implantation clinical studies, and two of these groups plan to have commercial retinal prosthesis systems available within the next 2 years. This paper reviews the development and current status of the most significant international retinal prosthesis research groups and discusses future prospects and issues associated with their retinal prosthesis systems.

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“…To overcome this problem, additional energy in the near infrared light was added to the spectrum of solar cells of the microphotodiode. 109 The infrared light is tolerated by the retina up to intensities of 200 mW/cm 2 , in contrary to the visible light (100 mW/cm 2 ). However, additional microelectronic circuitry to process and direct this power is necessary, and the concomitant heat dissipated by such a device may lead to retinal damage.…”

Section: How Much Heat Can the Device Produce?mentioning

confidence: 99%

Intraocular retinal prosthesis

Weiland

Humayun

2006

IEEE Eng. Med. Biol. Mag.

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Purpose: An electronic implant that can bypass the damaged photoreceptors and electrically stimulate the remaining retinal neurons to restore useful vision has been proposed. A number of key questions remain to make this approach feasible. The goal of this thesis is to address the following 2 specific null hypotheses: (1) Stimulus parameters make no difference in the electrically elicited retinal responses. (2) Just as we have millions of photoreceptors, so it will take a device that can generate millions of pixels/light points to create useful vision.Methods: For electrophysiologic experiments, 2 different setups were used. In the first setup, charge-balanced pulses were delivered to the retinal surface via electrodes inserted through an open sky approach in normal or blind retinal degenerate (rd) mice. In the second setup, the rabbit retina was removed under red light conditions from an enucleated eye and then maintained in a chamber while being superfused with oxygenated, heated Ames media. In both setups, stimulating electrodes and recording electrodes were positioned on the retinal surface to evaluate the effect of varying stimulation parameters on the orthodromic retinal responses (ie, recording electrode placed between stimulating electrodes and optic nerve head).For psychophysical experiments, visual images were divided into pixels of light that could be projected in a pattern on the retina in up to 8 sighted volunteers. Subjects were asked to perform various tasks ranging from reading and face recognition to various activities of daily living.Results: Electrophysiologic experiments: In a normal mouse, a single cycle of a 1-kHz sine wave was significantly more efficient than a 1-kHz square wave (P <.05), but no such difference was noted in either of the 8-or 16-week-old rd mouse groups (8-week-old, P =.426; 16-week-old, P =.078). Charge threshold was significantly higher in 16-week-old rd mouse versus both 8-week-old rd and normal mouse for every stimulus duration (P <.05). In all groups, short duration pulses (40, 80, and 120 s) were more efficient in terms of total charge (the product of pulse amplitude and pulse duration) than longer (500 and 1,000 s) pulses (P <.05). In all groups, applying a pulse train did not lead to more efficient charge usage (P <.05).Psychophysical experiments: In high-contrast tests, facial recognition rates of over 75% were achieved for all subjects with dot sizes of up to 31.5 minutes of arc when using a 25 x 25 grid with 4.5 arc minute gaps, a 30% dropout rate, and 6 gray levels. Even with a 4 x 4 array of pixels, some subjects were able to accurately describe 2 of the objects. Subjects who were able to read the 4-pixel letter height sentences (on the 6 x 10 and 16 x 16 array) seemed to have a good scanning technique. Scanning at the proper velocity tends to bring out more contrast in the lettering. The reading speed for the 72-point font is a bit slower than for the next smaller font. This may be due to the limited number of letters (3) visible in the window with t...

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Optimizing photodiode arrays for the use as retinal implants

Cited by 27 publications

References 8 publications

Fabrication of Flexible Binary Amplitude Masks for Patterning on Highly Curved Surfaces

Fabrication of Flexible Binary Amplitude Masks for Patterning on Highly Curved Surfaces

Current and future prospects for optoelectronic retinal prostheses

Intraocular retinal prosthesis

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