Implantable Devices for a Retinal Prosthesis: Design and Electromagnetic and Thermal Effects

FDTD;Finite-Difference methods;Alternating Direction Implicit (ADI);biomedical implants

Singh, Vinit ; Dr. Gianluca Lazzi, Committee Chair,Dr. Zhilin Li, Committee Member,Dr. Griff Bilbro, Committee Member,Dr. Mehmet Ozturk, Committee Member,Singh, Vinit ; Dr. Gianluca Lazzi ; Committee Chair ; Dr. Zhilin Li ; Committee Member ; Dr. Griff Bilbro ; Committee Member ; Dr. Mehmet Ozturk ; Committee Member

University:North Carolina State University

关键词: FDTD;    Finite-Difference methods;    Alternating Direction Implicit (ADI);    biomedical implants;   

Others  :  https://repository.lib.ncsu.edu/bitstream/handle/1840.16/5975/etd.pdf?sequence=1&isAllowed=y

美国|英语

来源: null

【 摘 要 】

A retinal prosthesis, wherein electrical stimulation isprovided to the retina of a person inflicted with outerretinal degenerative diseases such as Retinitis Pigmentosaand Age-related Macular degeneration, has been clinicallytested and has succeeded in providing limited vision; suchas shape recognition. It is hoped that an increasedelectrode count will improve visual acuity.The retinal prosthesis considered in this work is adual-unit system with an external (outside the human body)unit and an internal (inside the body) unit with a wirelesslink for power and data transfer between them. Such asystem poses possible health risks due to the incidentelectromagnetic energy of the wireless link and the powerdissipated by the internal components, particularly theprocessing chip which drives the electrodes responsible foreliciting a neural response from the retina. Tissue damagevia heating is one the primary concerns for such a systemmaking it necessary to obtain via simulation andin-vivo and in-vitro experiments,accurate estimates of thermal elevation due to theoperation of the such devices.In this work, numerical methods have been developed tocompute temperature increases and electromagnetic effectsdue to the prosthesis components in anatomically correcthuman head models. The explicit and theAlternating-Direction Implicit (ADI) Finite-DifferenceTime-Domain (FDTD) have been used. Further, a hybridexplicit-ADI method was developed for the heat equationwhich provided simulation speedup of more than 10x overconventional methods for the models considered.FDTD methods were employed to compute the induced currentdensities and Specific Absorption Rate (SAR) in the humanhead due the inductive link comprising the primary coil(external) and a secondary coil (internal). Differentorientations of the primary coil were considered in afrequency range of 1 MHz-20 MHz to provide guidelines forchoosing eventual frequency and power parameters to conformto international safety standards. A novel displacementfield excitation method was used for the spiral primarycoil and verified with analytical results.In an effort to reduce the size of the internal unit and toallow integration of a patch antenna (for a separate datalink), and the active devices on a single substrate, a 3-Dtrench inductor geometry was investigated. To enablepatterning of structured surface, a custom experimentalsetup was designed and maintained to processa positivetone PEPR2400 electro-depositable photoresist.