Research Of The Biological Volume Conduction Energy Transfer Model

Implantable device is a kind of electronic equipment implanted in the body or organisms, primarily used to measure physiological and biochemical parameters, diagnose and treat certain diseases. It can also be used to replace the organs which lose function and realize direct measurement and control functions under the natural state of life in vivo. With microelectronic technology and signal processing technology rapid development, implantable devices are increasingly wider applications in clinical. For practical implantable electronic systems, long-term power supply is the most important question. Currently, there are two ways to supply power for implantable devices: One is battery-powered. It is necessary to re-implant surgery before limited battery energy depletion; it will not only bring great painful to patients, and expensive surgery. Second, electromagnetic induction power supply. The energy will be transferred to implantable devices by magnetic induction technology, but, the magnetic induction coupling coefficient is small, energy transfer efficiency is low, and has the radio-frequency interference to the nearby medical equipment.A possible plan which can solve the aforementioned power problems of implantable devices is the rechargeable batteries, which can transfer electrical energy in vitro into implantable devices by using volume conduction of biology organism to maintain long-term reliable operation. The new technology is called volume conductive energy transfer which is in a theoretical stage. The main problems are current transfer efficiency, energy transfer efficiency and the impact of current on biological tissue. This paper focuses on: how to improve the energy transfer efficiency and current transfer efficiency by electromagnetic method under the premise of not damage the skin tissue. Mainly include the following:①Studied the structure of biological tissue (especially the skin) and biological impedance characteristics, electrode materials and impedance contact with the skin. Established a model of volume conductive energy transfer by ANSYS V10 and simulated.②Analyzed the factors which impact implantable devices energy transfer efficiency according to simulation results, and propose the reference to improve energy transfer efficiency.1)The energy transfer efficiency of rectangular electrode is higher than that of the circular electrode in volume conductive energy transfer system.2)The appropriate distance between electrodes in vitro of implantable devices is 2cm; the appropriate implantation depth is 4mm.3)The energy transfer efficiency is higher when frequency is 1kHz~100kHz in volume conductive energy transfer process.