Multiple-Unit Artificial Retina Chipset
Dr. Elliot McGucken
Physics University of North Carolina at Chapel Hill / NC State University
Dr. Elliot McGucken's Ph.D. Physics Dissertation is called: MULTIPLE UNIT ARTIFICIAL RETINA CHIPSET TO ADI THE VISUALLY IMPAIRED AND ENHANCED HOLED-EMITTER CMOS PHOTOTRANSISTORS
A computer-chip based device that can provide limited-resolution visionfor people with retinal-based blindness. Beneficiaries would be 10,000,000people worldwide suffering from forms of blindness including retinalpigmentosa and age-related macular degeneration.
MERRILL LYNCH "INNOVATION GRANTS" AWARDED TO FIVE DOCTORAL STUDENTS DOCTORAL RESEARCH YIELDS GROUNDBREAKING PROPOSALS RANGING FROM NEW COMPUTER CHIPS TO A MALE ORAL CONTRACEPTIVE
NEW YORK, Sept.16 -- The Merrill Lynch Forum today announced the firstwinners of the Innovation Grants Competition -- its global competitionchallenging doctoral students to craft commercial applications of theirdissertation research. The winners were recognized at an awards dinner atMerrill Lynch headquarters last night (Sept. 15), hosted by Merrill LynchChairman and CEO David H. Komansky.
Dr. Jan Mark Noworolski, from the University of California at Berkeley,received the top prize in the competition for creating a new type of powerconverter, a key element in virtually all electronic devices. Thistechnology would greatly reduce the size, parts count and weight of powersupplies for the increasingly pervasive array of portable electronicproducts such as cell phones and laptop computers, as well as enabling thedesign of new mobile electronic products. "Power management is one of themajor constraints in personal electronics," he said. "An integrated designusing this technology could offer a 10-fold improvement in deviceperformance."
A total of 213 proposals from 16 countries were submitted to thecompetition, which was open to new Ph.D. recipients in the sciences,liberal arts, and engineering disciplines. Entries were judged by adistinguished panel of nine entrepreneurs, venture capitalists,journalists, and innovators and were considered without knowledge of theapplicants' identity or academic affiliation.
"Academic research is a significant and often untapped source ofintellectual capital in our society, and a tremendous economic resource,"said Merrill Lynch Chairman and CEO David H. Komansky. "The winningproposals from this competition are all excellent examples of how newknowledge can be transformed into new value simply by encouragingresearchers to look at their research from a different perspective. Wehope that these Innovation Grants will help foster a closer interactionbetween world-class science and the world of commerce," Mr. Komanskyadded.
The judging panel consisted of:
John Seely Brown, Chief Scientist, Xerox Corporation, and Director, XeroxPalo Alto Research Center Edgar W. K. Cheng, former Chairman, The StockExchange of Hong Kong John Doerr, Partner, Kleiner Perkins Caufield &Byers Esther Dyson, Chairman, EDventure Holdings, Inc. Peter C. Goldmark,Chairman and Chief Executive, The International Herald Tribune WilliamHaseltine, Chairman & CEO, Human Genome Sciences, Inc. John Markoff,Technology Correspondent, The New York Times Edward McKinley, President,E.M. Warburg, Pincus & Company International, Ltd. Arati Prabhakar, formerChief Technology Officer, Raychem Corporation In evaluating theapplications, the judges sought to identify proposals with the potentialto affect real change in industries and in the way people live theirlives. "The Innovation Grants Competition is a terrific idea," said judgeJohn Doerr, of venture-capital firm Kleiner Perkins Caufield & Byers. "Iwas impressed with many of the proposals and thought that several of theideas would merit a venture-capital follow-up."
The five winning entries:
First Place, $50,000 -- Single-Chip Power Converter. Dr. Jan MarkNoworolski, University of California at Berkeley. A unique, one-chip powerconverter that uses electromechanical energy instead of inductive energystorage. This technology could dramatically reduce the size and complexityof portable electronic devices such as laptop computers, cellular phones,and pagers.
Second Place, $20,000 -- Membrane Chips. Dr. Jay T. Groves, StanfordUniversity. A technology that enables biological membranes to beincorporated into computer chips. These chips could be used by the medicaldiagnostic industry, particularly for AIDS research, and leukemia.
Second Place, $20,000 -- Multiple-Unit Artificial Retina Chipset (MARC).Dr. Elliot McGucken, University of North Carolina at Chapel Hill/NC StateUniversity. A computer-chip based device that can providelimited-resolution vision for people with retinal-based blindness. Thisdevice could benefit the more than 10,000,000 people worldwide sufferingfrom blindness originating from various causes.
Third Place, $10,000 -- Male Oral Contraceptive. Dr. Bruce Lahn, WhiteheadInstitute of Biomedical Research, Massachusetts Institute of Technology.This research led to the development of an understanding of the role ofthe gene CDY in producing an essential enzyme for sperm production. Thisresearch could produce a male oral contraceptive that would chemicallyinhibit the production of the sperm-producing enzyme.
Third Place, $10,000 -- Artificially Engineered Quantum Solid Materials.Dr. Alexander Balandin, University of Notre Dame. This study of newmaterials based on quantum confinement properties suggests opportunitiesfor the engineering of a new generation of electronic devices. The mostsignificant market application would be the improvement of devices such assemiconductor lasers, CD players, digital cameras, and optical drives.
Additional grants of $5,000 were awarded to each of the winners'universities and discretionary grants of $3,000 each were awarded to fiveadditional proposals.
The 1998 Innovation Grants Competition was directed by Michael Schrage, aResearch Associate at the MIT Media Lab, and a leading expert on issuessurrounding innovation and new business development. "What fuels the 'neweconomy' of the information age is ideas," said Schrage. "This competitiontakes great ideas that might otherwise have languished for years inacademia and brings them to the attention of people who can translate theminto transformative technologies. Anyone looking at these proposals cansee that they contain truly exciting possibilities."
The competition was open to doctoral students who successfully defendedtheir dissertations between January 1, 1996, and July 1, 1998. Entrantswere required to submit a 3,000-word explanation of how their dissertationtopic could be translated into a commercial product or service. Thedescription had to include: a summary of the dissertation, a descriptionof the most significant commercial idea embodied in it, an analysis of thepotential market for the product or service, and a discussion of technicalsteps necessary to bring the innovation to market.
The Merrill Lynch Forum is a "virtual" think tank established by theglobal financial services company to bring together leading experts toconsider and explore issues of worldwide importance in the areas oftechnology, economics, and international relations.
Those interested in additional information, should visit the Competition'sweb site, http://www.ml.com/innovation, or call 1-888-33Forum. Additionalinformation is also available by sending e-mail to:InnovationGrants@ml.com
BIOGRAPHIES
DR. ELLIOT MCGUCKEN
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Dr. Elliot McGucken was born and raised in Akron, Ohio, and he has studiedand taught physics ever since he left Akron to attend Princeton Universityas an undergraduate. He recently received his Ph.D. in physics from theUniversity of North Carolina at Chapel Hill (1998), where his research onthe Multiple Unit Artificial Retina Chipset To Aid The Visually Impairedoften led him down the road to North Carolina State University. He iscurrently continuing his involvement with the retinal prosthesis'sprototype development at NCSU, while also teaching physics and astronomyas an assistant professor of physics at the neighboring Elon College.
His favorite hobbies are celestial navigation, sailing and windsurfing,reading the classics, and writing poetry. Dr. McGucken received the TannerAward for Excellence in Undergraduate Teaching while at the University ofNorth Carolina at Chapel Hill, where he also received an honorarymembership in the the American Society of Physics Teachers.
Multiple Unit Artificial Retina Chipset (MARC) to Aid the VisuallyImpaired By Elliot McGucken
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1. Summary of the dissertation Engineering progress relating to thedevelopment of the multiple-unit artificial retina chipset (MARC)prosthesis to benefit the visually impaired is presented in mydissertation, "Multiple Unit Artificial Retina Chipset to Aid the VisuallyImpaired and Enhanced CMOS Phototransistors." The design, fabrication, andtesting of the first generation MARC VLSI chips are reported on. Asynthesis of the engineering, biological, medical, and physical researchis offered within the presentation of methods and means for the overalldesign engineering, powering, bonding, packaging, and hermetic sealing ofthe MARC retinal prosthesis. The retinal prosthesis is based on the fundamental concept of replacing photoreceptor function with an electronic device1, which was initiated by2 and has been extensively developed3,4 byMARC team-members Dr. Humayun et al.
The use of an inductive link forpower and telemetric communications is explored, and an experimental studyof RF coil configurations, showing their feasibility for this retinalimplant, is offered. An enhanced CMOS phototransistor with a holed emitter(HEP), used in the first generation MARC, is presented, along with anumerical model which also predicts its enhanced quantum efficiency. Dueto the small size of the intraocular cavity, the extreme delicacy of theretina, and the fact that the eye is mobile, an artificial retinal implantposes difficult engineering challenges. Over the past several years all ofthese factors and contrasts have been taken into consideration in theengineering research of an implantable retinal device. Initial steps3 towards fabricating a commercially available, implantable MARC device have been taken by our team of engineers, physicists, and doctors.
2. Description of the most significant commercial aspect
A multiple-unit artificial retina chipset (MARC) would create a newmarketplace by offering a cure for forms of blindness including retinalpigmentosa (RP) and age-related macular degeneration (AMD), which afflictover 10,000,000 people worldwide. Clinical studies4 have shown thatcontrolled electrical signals applied to a small area of a dysfunctionalretina with a microelectrode can be used to initiate a local neuralresponse in the remaining retinal cells. The neural response, orphosphene, is perceived by otherwise completely blind patients as a smallspot of light, about the size of a match-head held out at arm's length.When multiple electrodes are activated in a two-dimensional electrodearray, an image may be stimulated upon the retina. The MARC systemconsists of an extraocular means for acquiring and processing visualinformation, a means for power and signal transceiving via RF telemetry,and a multiple-until artificial retina chipset. The stimulating electrodearray is mounted on the retina with metal-alloy retinal tacks while thepower and signal transceiver is mounted in close proximity to the cornea.An external miniature low-power CMOS camera worn in an eyeglass framecaptures an image and transfers the visual information and power to theintraocular components via RF telemetry. The intraocular prosthesis willdecode the signal and electrically stimulate the retinal neurons throughthe electrodes in a manner that corresponds to the original imageperceived by the CMOS Camera.
3. Description of the market for the proposed product and the competition
The multiple-unit artificial retina chipset (MARC) is designed to provideuseful vision to over 10,000,000 people blind because of photoreceptorloss due to partial retinal degeneration from diseases such as Age RelatedMacular Degeneration (AMD) and Retinitis Pigmentosa (RP). People who arecompletely blind will initially gain the ability to discern shapes andpictures, and even to read, with limited resolutions of 15x15 pixels.Future MARC generations will provide greater resolutions, and the devicewill chart a brand new marketplace a s a prosthetic device to aid thevisually impaired.
3.1 Unique value derived by the customer
Before embarking on the MARC chip design, it was necessary to assess howuseful a limited-resolution view would b to the blind. Simple visualfeasibility experiments have been conducted at NCSU so as to determine howwell sight could be restored with a 15x15 array of pixels, each of whichwould be capable of four-bit stimulation, or sixteen gray levels. Apicture from a video camera was projected onto a television screen at thelow resolution of 15x15 pixels. When subjects who wore glasses removedtheir glasses, or when those with good sight intentionally blurred theirvision, the natural spatial-temporal processing of the brain allowed themto actually distinguish features and recognize people. When the subjectfocused on the screen, it appeared as a 15x15 array of gray blocks, butwhen the subject "trained" themselves to unfocus their vision, they wereable to "learn" to see definitive edges and details such as beard, teeth,and opened or closed eyes. These results are reminiscent of theexperiences with the artificial cochlear implant. When the artificialcochlear was originally being designed, it was believed that over 2,400electrodes would be needed to stimulate the nerves in a manner that would be conducive to hearing. Today, however, within a few weeks of receivingan implant, a patient can understand phone conversations with anartificial cochlear that has only six electrodes. One of the advantages ofthis project is that the MARC device will be interfaced with the world'sgreatest computer - the brain. The MARC won't be duplicating the exactfunctioning of the retina, but rather the device will be an entity thatthe brain will "learn" to use. A good analogy to think of is that inattempting flight, the Wright brothers did not attempt to imitate natureby building a plane which flapped its wings, but rather they did it in away that had not yet appeared in the natural world. Thus we believe that a15x15 pixel array will facilitate a level of sight which will be ofsignificant value to the patient. And after the initial prototype isdeveloped, there will be few barriers to stepping up the resolution.
3.2 Prior art, competition, and MARC advantages
The current design of the MARC clears several hurdles that exist is priorinventions and research. Much of the prior art has relied upon structuresso complicated or biologically intrusive as to make their implementationimpractical, and thus, to date, an operating implantable artificial retinahas not been achieved. Several international teams are actively pursuing aprosthetic device, including formidable competitors from MIT, a Germanteam of over 20 scientists and engineers who have received over$14,000,000 for the German government and a team from Japan who haverecently received government funding. To date, members of the MARC teamDr. Humayun et al. have been the only ones to electrically stimulate1,2,4controlled visual percepts human patients. Chapter 2 of my dissertationprovides a treatment of the papers, patents, and prior art embodied by thevarious teams' progress, but due to space limitations, only the advantagesof the MARC are presented here.
MARC Component Size: The novel multiple-until intraocular transceiverprocessing and electrode array-processing visual prosthesis allows forlarger processing chips (6x6 mm), and thus more complex circuitry. Also,by splitting the chips up into smaller components, and utilizingtechniques such as solder bumping to connect the chips with kaptonsubstrates, we shall keep the sizes to a minimum.
MARC Heat Dissipation: The power transfer and rectification, primarysources of heat generation, occur near the corneal surface, or at leastremotely from the retina, rather than in close proximity to the moredelicate retina.
MARC Powering: The novel multiple-until intraocular transceiver-processingand electrode array-processing visual prosthesis provides a more directmeans for power and signal transfer, as the transceiver microprocessingunit is placed in close proximity to the cornea, making it more accessibleto electromagnetic radiation in either the visible wavelength range orradio waves. Solar powering and especially RF powering are made morefeasible.
MARC Diagnostic Capability: The transceiver unit is positioned close tothe cornea, and thus it can send and receive radio waves, granting it thecapability of being programmed to perform different functions as well asgiving diagnostic feedback to an external control system. Diagnosticfeedback would be much more difficult with the solar powering.
MARC Physiological Functionality: Our device was designed in conformancewith the physiological data gained during tests on blind patients. We arethe only group who has yet created a visual percept (with electricalstimulation) in a patient. Therefore, we have the unique advantage ofdesigning around parameters which are guaranteed to work.
Reduction of Stress Upon The Retina: Our device would reduce the stressupon the retina, as it would only necessitate the mounting of theelectrode array upon the delicate surface, while the signal processing andpower transfer could be performed off the retina. Also, buoyancy could beadded to the electrode array, to give it the same average density as thesurrounding fluid.
Approximately 10,000,000 people worldwide are severelyvisually handicapped due to photoreceptor degeneration5 experienced inend-stage age-related macular retinal degeneration and retinitispigmentosa. In addition to benefiting the visually impaired, restoringvision to a large subset of blind patients promises to have a positiveimpact on government spending.
4. Description of the five most important technical steps
The honing and development of several aspects of the MARC system must yetbe fully realized so as to optimize the final device's functionality andperformance. Concurrent engineering tasks which are both touched upon andelaborated in chapters of my dissertation include the following:
The design, fabrication, and testing of the signal-processing andstimulus-driving MARC2, MARC3 and MARC46 VLSI chips and thevideo-processing chip. These are VLSI chips endowed with microprocessingcircuitry to encode and decode visual information, and drive thestimulating electrodes.
The enhancement of the CMOS photodetectors and the Holed EmitterPhototransistor. These are the fundamental building blocks of siliconphotosensors.
The final designs and optimization of the kapton/polyimide or siliconstimulating electrode array. Kapton polyimide flexible polymer which wouldallow for the fabrication of an electrode array which could conform to thecurvature of the retinal surface. So far it has proven to bebiocompatible.
The design and refinement of the RF telemetry system and video protocol.RF Telemetry is utilized to transmit both power and signal without thepresence of physical wires. Thus the device is entirely self-containedwithin the eye.
The bonding, packaging, and hermetic sealing of the CMOS signal-processingchips with the kapton electrode array. The hermetic packaging of a chronicdevice with over 100 electrical feedthroughs is a challenge. Theintegration of microelectronics with damaged or degenerated biologicalsystems in order to provide some of the lost function is a rapidlyemerging field, and we have been and will continue to share technologieswith other groups also working on biological prosthesises.
5. Description of how best to test prototypes
Extensive laboratory and clinical testing will be conducted beforefunctioning MARC is realized. The doctors on our team are conducting thebiocompatability and threshold-stimulation experiments within both humansand animals, while the engineers at NCSU-ECE are concentrating on thetesting of the functionality of the computer chips, and the performance ofthe RF telemetry transfer of power and signal. Hermeticity may be testedby submerging device in saline baths for extended periods.
In order to test MARC1, which was endowed with HEP photosensors, the imageof a while paper E mounted on black paper was focused onto the MARC chip.An adjustable incandescent light was shone onto both black and whitepaper, and the difference in reflected power was measured, and found to bearound a factor of ten. This order of magnitude difference is easilyrecognized by Mead's logarithmic photodetector circuit. Even though theimage of E was focused down to about 20% of its original size, so as tofit upon the chip, the difference between the intensities of theneighboring light and dark areas remained the same, as they were bothmultiplied by the same factor.
All the pixels which were subject to the light of the E's image fired,while those beyond the border remained off. The output from the "on"pixels, which resulted in 250 mA, 2ms pulses at a 50 Hz clock rate, weresufficient for retinal stimulation. The photosensing andcurrent-generating partition of the artificial retina chip has beentested, and it ahs been demonstrated to work. These results suggest thatthe chip would facilitate the perception of outlines where sharp contrastexisted, such as for windows or illuminated text. The Doctors havedemonstrated that the 5x5 electrode array functions, and the next steptowards an artificial retinal prosthesis is to connect the dual unitvisual prosthesis to the 5x5 electrode array, and implant the dual unitdevice in an animal, so as to test biocompatibility.
6. Description of the limitations and challenges in the MARC project
The MARC project spreads itself across a diverse array of scientific,engineering, and medical disciplines. Perhaps one of the greatestchallenges associated with this project is the interdisciplinary nature ofthe device's design, which requires the devotion from members of a large,unified team from a wide array of disciplines and distant institutions.One of the goals of my dissertation was to aid the project by providing anoverview or synthesis of the wide-ranging research, within thepresentation of the complete system engineering of the MARC implantableprosthesis. The inter-disciplinary challenge involves the fabrication ofthe processing chips, the acquisition and transmission of visual data in away that is meaningful to the device and to the patient, a wireless powersource, and a form of biocompatible, hermetically-sealed packaging. TheMARC designs presented throughout my dissertation attempt to integrate themultifaceted technologies in a final device that will be beneficial to avisually-impaired patient.
As we approach a functioning MARC prosthesis, the design will continue toevolve, as the refinement of any one parameter affects all the rest. Forinstance, should the main intraocular chip be subdivided into smallerindividually-sealed chips so as to reduce the risk of realizing a completesystem failure if one chip should malfunction, the basic chip design, aswell as the hermetic packaging, will have to be altered. An alteration inthe hermetic packaging will affect where the chip may be mounted. Adifferent chip design will require a different power source and thustelemetry configuration. And a different telemetry configuration may alterthe coil designs, which would affect the size of the external battery.Thus an alteration in any one aspect of the design resounds throughout theentire system. The purpose of this dissertation was to offer an overviewof all the parameters affecting the design of the MARC, elaborate on allthe engineering progress that has been made, anticipate design andengineering hurdles, and suggest approaches for future research.
The photosensing/current-generating component of the artificial retinachip has been tested, and it has been demonstrated to work. Investigationsinto the feasibility of RF powering have so far been positive. Theelectrode design is being honed, and the Doctors have demonstrated that a5x5 electrode array can stimulate simple pictures upon a patient's retina.The doctors are currently investigating ways of stimulating the retinawith lower currents, which will have a positive impact on the design ofthe chip and RF powering system.
The next step towards an artificial retinal prosthesis will be to developthe second and third generation MARCs which will be capable of driving a15x15 electrode array and 25x25 electrode arrays, and testing the devicesfor short periods within a human. The implications of this research mayextend beyond this immediate project, as contributions to the overallfield of implantable prosthetic devices and hermetic packaging. Theobservations and clinical and engineering experiments performed shouldlend insight into the actual functioning of the human retina. The feedbackgained by these studies should provide a vehicle for further understandingof the retinal/vision/perception process.
In addition, a CMOS phototransistor which exhibits an enhanced quantumefficiency was also developed, and a numerical model was presented whichalso predicts its enhanced efficiency. The enhanced performance isaccounted for via the physics of transistor operation. The CMOSphototransistor may find an application in the emerging field of CMOSphotodetectors, wherein researchers are attempting to create low-poweredinexpensive cameras.
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References: 1 E.D. Juan, Jr. Mark S. Humayun, Howard D. Phillips; "RetinalMicrostimulation," US Patent #5109844, 1993
2 M. Humayun, "Is Surface Electrical Stimulation of the Retina a FeasibleApproach Towards The Development of a Visual Prosthesis?" Ph.D.Dissertation UNCCH BME 1994
3 W. Liu, E. McGucken, K. Vichiechom, M. Clements, E. De Juan, and M.Humayun, "Dual Unit Retinal Prosthesis," IEEE EMBS97
4 M.S. Humayun, E.D. Juan Jr, G. Dagnelie, R.J. Greenberg, R.H. Propst andH. Phillips, "Visual Preception Elicited by Electrical Stimulation ofRetina in Blind Humans by Electrical Stimulation of Retina in BlindHumans," Arch. Ophthalmol, pp. 40-46, vol. 114, Jan. 1996.
5 Research to Prevent Blindness, Progress Report 1993.
6 K. Vichiechom, M. Clemments, E. McGucken, C. Demarco, C. Hughes, W. Liu,MARC2 and MARC3 (Retina2 and Retina3), Technical Report, February, 1998
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