Resonant coupling energy transmission technology and its applications to implanted medical devices

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Resonant coupling energy transmission technology and its applications to implanted medical devices


Author: Wang, Junhua
Title: Resonant coupling energy transmission technology and its applications to implanted medical devices
Degree: Ph.D.
Year: 2012
Subject: Implants, Artificial -- Power supply.
Electric power transmission.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Electrical Engineering
Pages: xviii, 184 p. : ill. ; 30 cm.
Language: English
InnoPac Record:
Abstract: Due to the development of power electronics and magnetic materials, replacing conventional wire energy transmission in electrical power systems with non-contact, inductive couplings becomes possible. The technology of transferring energy through electromagnetic field opens the door to a new age of rotating, sliding, and separable couplings. Inductive couplings can offer safe, reliable, and efficient power transmission that is largely immune to the effects of wear and the environment. Inductive charging transfers energy from the transmitter to the receiver by inductive coupling. A transmitter sends energy through inductive coupling to an electrical device, and then the energy is stored in the batteries. Because there is a gap between the two transmitting and receiving coils, inductive charging falls into one kind of certain-distance wireless energy transfers. The implanted medical devices, including cardiac pacemaker and cardioverter defibrillator, are now increasingly being used in the therapeutic treatment for cardiac arrests. However the power supply arrangement, hitherto, of the implanted medical devices are far from satisfactory. A new technology called witricity for wireless energy transmission over a fair distance as reported by Massachusetts Institute of Technology (MIT) in July of 2007 provides a new possibility to overcome the above difficulties. The method is based on the well known principle of resonant coupling, which stipulates the coupling between the resonant objects of the same resonant frequency, while reduces the coupling with other off-resonant environmental objects. However, the MIT's receiver has the same size as the transmitter (with a diameter of 600 mm). In implanted medical devices, the receiver must be very small in order to be implanted and housed within the patients' thoracic cavity. In the MIT design, the receiver size cannot be scaled down easily because the receiver dependents on the distributed capacitance of the coils. Therefore, there are many challenges in the applications of this basic theory to implanted medical devices.
This thesis intends to develop a wireless energy transmission system based on witricity technology for powering and recharging the implanted medical devices. A resonant coupling energy transmission system which is specially designed for implanted medical devices is thus proposed with different geometry structures including circular coil, ring-shaped coil, and rectangular coil have been designed. Special coils with the same resonant frequency of the transmitter and the receiver have been fixed that the energy transmission efficiency can be greatly increased and the size of the receiver is substantially reduced. Electromagnetic field and electric circuit coupled models have been built based on Ansoft HFSS and Ansoft designer. The experimental prototypes have been constructed to test the performances of the witricity energy transfer system. In the thesis, three practical witricity systems with different geometry structures have been designed specially for electrical devices. We used the developed program and numerical models to capture the entire behaviors of the system from transmitter to receiver including the power source circuit and charging circuit through co-simulation with the electromagnetic field. The experimental prototypes for the study of electrical energy delivery between an electric implant and an external charger have been constructed. The new energy transmission system has high efficiency, long transfer distance, good robustness, low insensitivity to misalignment and line-of-sight interruption. In vitro performance tests have been realized using a physical thorax phantom to verify its effectiveness.

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