Design and implementation of hybrid acoustic energy transfer technique for wireless pacemaker system

Abstract

Miniaturized biomedical devices have drawn significant industrial attention due to their convenient geometry. In addition, these devices have improved and continuous functionality with longer lifetime, and reliable power supply, especially for implanted devices. However, they contain batteries in order to activate the systems, which is bulky, cost inefficient, not rechargeable and need frequent replacement. Hence, removing the battery from the system has been an active research area for last two decades. To resolve, wireless power transfer (WPT) technology has been proposed in real practice. So far, WPT has adopted 4 modules to function, namely, inductive WPT, capacitive WPT, optical WPT and acoustic energy transfer (AET). All but AET, suffer from the safety or performance issues. However, AET itself is influenced by several parameters which results affected system performances. Consequently, this research work proposes an approach based on the acoustic energy propagation method to deliver power to implantable devices wirelessly. To do so, the proposed system is actuated by the pair of piezoelectric devices, which are the transmitter and receiver. The main contribution of the work relies on the use of same device platform for two energy harvesting scheme, acoustic and electromagnetic. It is called, hybrid AET (HAET). In addition, a simulated human chest phantom is presented to investigate the impact of multilayer propagation medium. Several parameters can be treated as the evaluation criteria; however, received power, operating frequency, device geometry, separation distance is mainlyfocused mainly in this research. Hence, they are addressed in detail with several finite element analysis, including classical model analysis, vectorial descriptions and computer aided simulations. Lastly, the design is tested under real environment for post fabrication verification and proof-of-concept characterization. The receiver device dimension is selected as 20×10×0.62 mm3. From the mathematical modeling and the finite element analysis, it is found that, the proposed HAET can deliver 2 mW power to the receiver end in the pacemaker. In addition, the achieved efficiency is 2.77% which is better compared to most of the existing literatures. However, the solution for acoustic reflection coefficient and impedance mismatch for a multilayered medium is still a challenge. Additionally, the impact of the heartbeat on the receiving energy harvesting is not considered in this research.