BIONIC EYE POWERED BY NANOGENERATOR Design of electronic eye for visually impaired

Praveenkumar Narayanan Department of Electronics and Instrumentation

Panimalar engineering college Chennai, India

Praveen892000@gmail.com

Guhan Senthil Department of Electronics and Communication

Panimalar engineering college Chennai, India

guhan.senthil@yahoo.com

Abstract—Bionic eye is an artificial electronic eye. The main purpose of bionic eye is to provide vision, partially to the visually challenged people by the use of modern day electronic devices like charge coupled device (CCD) camera and bionic eye implant. The implant is a small chip that is surgically implanted behind the retina in the eye ball. It could restore the eye sight of the people who suffer from age related blindness. There are two basic methodologies of bionic eye, multiple unit artificial retina chip system (MARC) and artificial silicon retina system (ASR). However, this paper presents a novel idea of integrating a new approach of bionic eye with the nanogenerator. The nanogenerator is multifaceted when compared to the external batteries providing better power, compactness and higher efficiency. The potential advantage of proposed method is to be able to remove the blindness to a feasible extent by making advance in the present research and improving manufacturing technology.

Keywords-bionic eye; artificial eye; nanogenerator applications; electronic eye; Retina damage; eye replacement; blindness

I. INTRODUCTION Bionic eye is a bio-electronic eye. Bionic eye replaces the

functionality of a part or whole of the eye. An external camera is worn on a pair of dark glasses which sends the images in digital form to the radio receiver placed in the eye. The radio receiver is attached to the implant chip on the retina. The implantation is of two types, epiretinal implant and subretinal implant, based on whether the implant is placed on or behind the retina. In our proposed method of bionic eye, a small and a powerful camera powered by nanogenerator, is implanted inside the patient’s eye rather than worn on a pair of glasses. The camera is small and consumes very low power.

A. The Human eye : Structure and function The Human eyes operate on the same principle as that of

a camera. The Human eye is an organ that reacts to light for several purposes. The Human eye ball is roughly spherical in shape. The important part of the eye responsible for the vision is the retina. The retina is a light sensitive tissue lining the inner surface of the eye. Light falling on the eye is focused on to a sheet of light sensitive cells. The photosensitive ganglion cells in the retina that receive the light signals affect the adjustment of the size of the pupil. The ganglion cells are connected to the rods and the cone

cells in the retina. The cone cells are responsible for colour recognition of the image viewed and the rod cells distinguish the movement and the contrast of the image on the retina. The retina is connected to a nerve called the optic nerve that connects the brain and the eye. The eye ball is placed in a protective cone shaped cavity in the skull called the orbit or the socket and measures approximately one inch in diameter.

Figure 1. Human eye structure.

Fig. 1 shows interior structure of the human eye in its basic form. The light signals enter the eye through the cornea. The cornea focuses the rays of light falling on eye. The light then passes the pupil and the lens of eye, which leads to the formation of an inverted image on the retina of the eyeball. The retina sends electrical signals to the brain through the optic nerve. The brain interprets the signals sent from the retina and forms the image.

B. Basic Eye Disorders The Eye disorders dealt here are listed below: • Retinitis Pigmentosa • Macular Degeneration

1) Retinitis Pigmentosa Retinitis Pigmentosa (RP) is the name given to a group of

hereditary diseases of the retina of the eye. RP is a progressive blinding disorder of the outer retina which involves degeneration of neurons [1]. RP may be caused by a breakdown in the function of the rods or the cones in some part of the retina. The retina is so complex that, breakdowns may occur in a variety of ways and so RP is not a single

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2011 International Conference on Life Science and Technology IPCBEE vol.3 (2011) © (2011) IACSIT Press, Singapore

disorder but a great number of disorders. The breakdown of cone function may be called Macular Degeneration.

2) Macular Degeneration

Macular Degeneration is a medical condition which usually affects older adults. Macular Degeneration is mainly due to the breakdown of the cones in the retina. The cone cells are responsible for distinguishing the colours of the image formed on the retina. In macular degeneration, a layer beneath the retina, called the retinal pigment epithelium (RPE), gradually wears out from its lifelong duties of disposing of retinal waste products. A large proportion of macular degeneration cases are age- related and it can make it difficult to read or recognize faces, although enough peripheral vision remains to allow other activities of daily life. Age related Macular Degeneration (AMD) usually affects people over the age of 50 and there are two distinct types - wet AMD and dry AMD. Wet AMD results from the growth of new blood vessels in the choroids, causing an accumulation of fluid in the macula which leads to retinal damage. Dry AMD represents at least 80% of all AMD cases and results in atrophy of the Retina. Usually yellowish-white round spots called drusen first appear in a scattered pattern deep in the macula [1].

II. BIONIC EYE A visual prosthesis or bionic eye is a form of neural

prosthesis intended to partially restore lost vision or amplify existing vision. It usually takes the form of an externally-worn camera that is attached to a stimulator on the retina, optic nerve, or in the visual cortex, in order to produce perceptions in the visual cortex. Fig. 2 shows the schematic diagram of the bionic eye system.

Figure 2. Bionic eye system.

A. Artificial silicon retina Artificial Silicon Retina (ASR) is a solid state

biocompatible chip which contains an array of photoreceptors, and is implanted to replace the functionality of the defective photoreceptor. The ASR is a silicon chip 2 mm in diameter and 1/1000 inch in thickness. It contains approximately 3,500 microscopic solar cells called micro photodiodes, each having its own stimulating electrode. These micro photodiodes are designed to convert the light energy from images into thousands of tiny electrical impulses to stimulate the remaining functional cells of the

retina in patients suffering with AMD and RP types of conditions. Current generated by the device in response to the light stimulation will alter the membrane potential of the overlying neurons and thereby activate the visual system.

Figure 3. ASR system.

Fig. 3 shows the ASR methodology in the bionic eye system. The ASR is powered solely by incident light and does not require the use of external wires or batteries. When surgically implanted under the retina, in a location known as the sub retinal space, the ASR is designed to produce visual signals similar to those produced by the photoreceptor layer. From their sub retinal location these artificial "photoelectric" signals from the ASR are in a position to induce biological visual signals in the remaining functional retinal cells which may be processed and sent via the optic nerve to the brain.

1) Creation of artificial sight A visually challenged person can be made to see light by

stimulating the ganglion cells behind the retina by passing electrical signals. The nerves behind the retina function even after the retina degenerates. Hence, scientists set out to create a device that could translate images and electrical pulses that could restore vision.

Figure 4. ASR on a penny.

Fig. 4 shows ASR on a penny. The dot above the year on the penny is the full size of the ASR. As you can see in the picture at the top of this page, the ASR is an extremely tiny device, smaller than the surface of a pencil eraser. It has a diameter of just 2 mm (.078 inch) and is thinner than a human hair. In order for an artificial retina to work it has to be small enough so that doctors can transplant it in the eye without damaging the other structures within the eye.

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A. Nanogenerator powersupply Nanogenerators are devices that are made up of Zinc

oxide nanowires which when bent and released produce electric charges [3]. By building interconnected arrays containing millions of such nano wires, we can produce enough power supply for small scale devices [4]. Fig. 9 shows the internal structure of the nanogenerator, which consists of the PZT nanofibers placed on the silicon substrate.

Figure 9. Nanogenerator structure.

In the case of the proposed method, the nanogenerator is used on the blood vessels to produce the sufficient potential to run the camera and the transmitter on the printed circuit board. Fig. 10 shows the nanogenerator in a crystal casing.

Figure 10. Nanogenerator in a crystal casing.

B. Prosthetic eye The prosthetic eye consists of a printed circuit board

(PCB) placed in between the lenses set in the front part of the eye replacing the iris and the lens in the human eye [5]. The

PCB is responsible for capturing the images of the viewer and processing the captured images into digital signals, compressing and transmitting them to the retinal implant. Fig. 11 shows the printed circuit board where the size of the PCB is compared to that of a 1 cent coin.

Figure 11. Printed circuit board.

C. Proposed system functionality The working of the proposed system is explained as

following. The camera captures the images of the viewer and converts the analog images into digital signals and compresses it. The digital image signals are then sent via the transmitter through the wires to the retinal implant on the retina. The retinal implant is connected to the optic nerve of the brain. The brain forms the image with the electrical signals obtained from the retinal implant. Fig. 12 shows the schematic diagram of the proposed system of bionic eye.

Figure 12. Proposed bionic eye system in the eyeball.

IV. CONCLUSION Bionic devices are being studied and worked upon to do

more than replacement of the defective parts. Bionic Eye is a system that is still under research. Providing power to run the bionic eye implants has been a major challenge for the researchers. With the upcoming development in the field of nanotechnology, Nanogenerators are the future of power supply for small scale devices. The major advantages of the proposed bionic eye system are listed below:

• The Patient does not have to carry external batteries along and the lifetime of the power supply is more.

• The system becomes more compact and efficient. • There will be no external wiring to the human body.

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REFERENCES [1] Asher,A.;Segal,W.A.;Baccus,S.A.;Yaroslavsky,L.P.;Palanker,D.V.,

“Imageprocessing for A High-Resolution Optoelectronic Retinal Prosthesis”, IEEE transactions on Biomedical Engineering, vol. 54, no. 6,pp. 993-1004, June 2007

[2] M.S Humayun , J.D Weiland , G.Chader , ”Basic research , biomedical engineering and clinical advances”,2007,pp. 151-206.

[3] Xi Chen,Shiyou Xu,Nan Yao and Yong Shi, ”1.6v nanogenerator for Mechanical Energy harvesting using PZT nanofibers”, Nano Letters 2010, 10, pp. 2133–2137

[4] Guang Zhu, Rusen Yang, Sihong Wang and Zhong Lin Wang, School of Materials Science and Engineering, Georgia Institute of technology,Atlanta,Georgia,“Flexible High-Output Nanogenerator based on lateral ZnO Nanowire Array”, Published, Copyright © American chemical Society .

[5] Kosta Grammatis,Rob Spence, “Building the bionic eye; Hacking the human”, Future of Journalism conference, www.eyeborgproject.com .

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