Abstract As one of the optimal solutions to cardiac pacemaker energy supply, MCR-WPT is still in the research stage and has not qualified for clinical application. In response to the low transmission efficiency and poor deflection resistance of wireless energy supply systems for cardiac pacemakers, a wireless energy supply system based on hybrid mu-negative metamaterials was proposed. The coupling effect between coils is enhanced via the LC resonance generated by the metamaterial periodic structure, and the transmission performance of the MCR-WPT system can be improved without adding cumbersome control measures and a complex magnetic coupling mechanism. First, based on the resonance principle and quality factor theory of mu-negative metamaterials, two MNG units with different resonant frequencies were designed. Secondly, the relationship between the negative permeability and the magnetic loss of the units was analyzed along with the magnetic leakage status of the WPT system. Based on the analyses, the hybrid MNG slab with two negative permeabilities was constructed and applied to a wireless energy supply system for cardiac pacemakers. Thirdly, the peak electric field intensity and peak specific absorption rate of human body tissues were calculated with finite element analysis software to prove the safety characteristics of the system. Finally, an experimental platform of a wireless energy supply system for pacemakers was built to verify the polymagnetic properties of the hybrid MNG slab, and temperature rise experiments were added further to verify the safety and feasibility of the system. Experimental results show that the system output power is enhanced from 0.19~0.81 W to 1.02~1.67 W, and the transmission efficiency is improved from 8.53 %~43.15 % to 40.78 %~57.32 % under the case of 16~28 mm spacing between the transmitting and receiving coils. When the receiving coil is 20 mm away from the transmitting coil with horizontal offset in three directions, the output power of the MCR-WPT system incorporating the hybrid MNG slab is improved by 0.35 W, 0.55 W, and 0.64 W, and the transmission efficiency is improved by 15.05 %, 18.13 %, and 20.57 %. A minimum output power of 0.86 W and a minimum transmission efficiency of 32.81 % can be maintained. The offset-resisting ability of the power transfer system is significantly improved. Considering the actual working conditions of the implantable wireless energy supply system, a 30 min simulated charging test was conducted, and the maximum temperature rise of the system was 3.49 ℃, which has no personal injury. Meanwhile, according to the simulation results, the peak electric field intensity of human tissue of the MCR-WPT system incorporating the hybrid MNG slab was 41.5 V/m, and the peak specific absorption rate was 1.16 W/kg, lower than the international radiation. The safety characteristics of the system are verified. The following conclusions can be drawn from simulations and experiments: the hybrid MNG slab proposed in this paper enhances the transmission efficiency and offset resistance of the wireless power supply system for cardiac pacemakers. Therefore, adding metamaterials is an appropriate method to improve the performance of pacemakers with the WPT system. As the coil spacing of the MCR-WPT system increases, the hybrid MNG slab improves the performance of the system more obviously. Therefore, the proposed hybrid MNG slab is also suitable for the wireless power supply system of implantable medical devices (e.g., capsule endoscope) working at longer distances.
Chen Weihua,Hou Haitao,Yan Xiaoheng等. Wireless Energy Supply System for Cardiac Pacemaker Based on Hybrid Mu-Negative Metamaterials[J]. Transactions of China Electrotechnical Society, 2023, 38(4): 865-878.
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2023, Vol. 38 
