Energy Supply Through Volume Conduction And Simulation Of Implantable Devices

The power supply is a common concern for implantable devices whose purpose is to maintain long-term, stable and reliable operation, and achieve its intended function. There are several possible approaches to power implants,however,only battery and magnetic inductive coupling are practical.The service life of an implantable device powered by a battery is short because of the limited battery capacity.The conversion efficiency of magnetic inductive coupling in power delivery is generally poor due to the energy loss in conductive biological tissue, and magnetic inductive coupling can causes RF interference to nearby medical instruments.In order to avoid the major drawback of magnetic inductive coupling method and expand the service life of implantable devices, scholars at home and abroad presents the energy delivery process based on volume conduction across skin and connective tissue.Through the electrode close to the skin in vitro, this technology is making use of biological organization ionic fluid as the carrier to transfer the energy of excitation power in vitro to the electrode in vivo, and then supply power for implantable electronic devices in vivo or charge the rechargeable battery.the electrode design and impedance distribution of Electrode skin cell skin is the key technology affecting the system performance.According to circuit technology and electromagnetic field analysis method, scholars at home and abroad build a mathematical model of the system and make use of fresh pig skin as experimental material to verify its feasibility.However,there is not an effective electrode design and optimization method of skin electrode impedance distribution for the energy transfer technology.On the basis of Volume conduction energy transfer technology at home and abroad,this paper focuses on Volume conduction technology addressed above,uses circuit technology analysis method build the circuit model, builds Volume conduction model In the finite element software COMSOL Multiphysics, carrys out the Optimization study on the shape and layout of the electrode and the impedance distribution of the electrode skin cells, establishes a system optimization program, and realizes the purpose that using conductive characteristics of body tissue to transfer the power in vitro across skin to the rechargeable battery of medical implanted devices in vivo by Energy coupling.implemented by, the skin will cross through coupling energy passed into the body of medical implant devices on。Taking into account the characteristics of electrode polarization and ionic conduction current,use AC power as the excitation power of volume conduction energy delivery system.①The paper introduced electric conduction principle and equivalent circuit of biological tissue, energy transfer technical solution, and it analyzed the structure and electrical properties of human skin.②Energy delivery model of volume conduction was created by COMSOL Multiphysics, electric potential and current density through skin also can be calculated.③Study excitation power technology of Volume conduction energy delivery system.there is a close link between the electrical properties of biological tissues and the frequency of excitation power.different power frequency and amplitude was applied to the electrode out of the model.The transmission current transmission efficiency and energy transfer efficiency of the systems were calculated.The energy transfer characteristics of the system can be the best by using appropriate excitation powe.④In this paper,different electrode shapes were designed and their effects on the characteristics of the energy transfer system were studied.Focusing on symmetric electrode, three different electrode shapes were designed which were circular electrode, the rectangular and the fan-shaped.⑤The impedance of the electrode skin cells were distributed by changing model electrode section and the horizontal distance between the electrodes.The transmission current,current transmission efficiency and energy transfer efficiency inside and outside the skin cells were calculated.Analysis and summarize optimization of theimpedance distribution for the electrode skin cells.⑥The finite were built according to the optimization program of the system and the effectiveness of the program were verified.According to the simulation results that current transfer efficiency up to 67.7% and Energy transfer efficiency of were up to 7.3% (much larger that of non-core electromagnetic induction)after re-optimizing the model in the situation of Ensuring human security. transfer current I1, I2In vitro and in vivo, respectively were 2.3mA and 1.5mA which did not exceed the current safety of the human body.The theoretical and simulation analysis show that the the optimization scheme of the system proposed in this paper can effectively improve energy delivery efficiency of the system.