THESIS
2019
xi, 50 pages : illustrations ; 30 cm
Abstract
For implantable medical devices (IMDs), the implant size is limited, so wireless power transfer is widely used to eliminate the use of batteries. A wireless powered trans-sclera electrical stimulation (TsES) system has been developed in previous research to treat retinal degenerative diseases. However, the power transfer efficiency of the prototype inductive link is only 8% at a distance of 10 mm, which is not enough for rabbit in vivo experiments. The secondary coil is also fabricated on a printed circuit board, and even coated with silicone, it is still too rigid to be used an implant. Finally, the implant biocompatibility cannot be guaranteed. In this thesis, several solutions are proposed to solve these three problems.
The implant size is critical and the operating distance is a fe...[
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For implantable medical devices (IMDs), the implant size is limited, so wireless power transfer is widely used to eliminate the use of batteries. A wireless powered trans-sclera electrical stimulation (TsES) system has been developed in previous research to treat retinal degenerative diseases. However, the power transfer efficiency of the prototype inductive link is only 8% at a distance of 10 mm, which is not enough for rabbit in vivo experiments. The secondary coil is also fabricated on a printed circuit board, and even coated with silicone, it is still too rigid to be used an implant. Finally, the implant biocompatibility cannot be guaranteed. In this thesis, several solutions are proposed to solve these three problems.
The implant size is critical and the operating distance is a few times larger than the secondary coil dimension, so it is difficult to maintain power transfer efficiency (PTE) at an acceptable level. However, increasing the implant size will cause patients pain or discomfort and complicate the implantation surgery. To solve the trade-off between the implant size and high PTE, we design an oval-shaped spiral secondary coil to fully use the implant size to increase the PTE so that the operating distance is increased to 11 mm.
To achieve a flexible implant, the secondary coil and the electrodes are fabricated on a polyimide-based substrate. A carbon thin film layer is evaporated on the surface of the electrode to improve biocompatibility. In vivo experiments on New Zealand rabbits are also discussed in this thesis.
Based on the in vivo experiments , which showed the PTE of our modified TsES system needed to be further increased, we proposea polyimide-based flexible 3-coil inductive power transfer link. An iterative design procedure is devised to obtain the optimal coil geometries of the 3-coil inductive link. A design example optimized for a 40.68 MHz carrier frequency with a coupling distance of 15 mm is presented. The results are verified through simulations and measurements.
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