Design, manufacture and performance characterization of wireless power transfer systems for biomedical devices

Abstract

Wireless biomedical devices have attracted the attention of researchers over the last decade for health monitoring, syndrome detection, disease prevention, drug delivery and prosthetic limb applications. However, the power requirement is the major constraint for the implementation of such devices. Packaged batteries are the traditional power source for these devices. This source of power is limited by the size and the life time which are the significant parameters for biomedical implants. In addition, any leakage from the battery can cause serious health hazard. Similarly, the transdermal or percutaneous wiring is inconvenient due to bulky size and risk of infection. Therefore, wireless power transfer technology has emerged recently as an alternative source of batteries and wired power supply for biomedical devices such as pacemakers, retinal implants and neurostimulators. The power requirement from some of these devices is however a major challenge. In this Ph.D. thesis, the designing, modelling and optimization of wireless power transfer (WPT) systems for biomedical applications are presented. Accurate and closed form expressions of self- and mutual inductances are derived and also verified experimentally. The translational and angular misalignments are considered for the mutual inductance expression. Furthermore, the parasitic components such as AC resistance and capacitance are analyzed for the modeling of the proposed WPT systems. The expression of the power transfer efficiency of the multi-transmitter (TX) is analyzed and derived. A nested multi dimensional optimization algorithm is utilized for the optimization of the proposed WPT systems for biomedical applications. Two 3-D WPT receiver (RX) coils with a flexible mutli-TX system are designed and manufactured for capsule endoscopy (CE). The RX coils are optimized to accommodate in an 11 mm diameter and 26 mm length typical capsule. The achieved PTE of more than 1% and tissue safety analysis constitute the proposed WPT systems as a potential candidate for the CE. Further, one of the proposed 3-D receivers is studied for the potential of the capsule localization and positioning using the received power of the WPT system. Additionally, a WPT system is proposed and successfully implemented primarily for prosthetic hand for the physically disabled people.