Exploiting Self-capacitances for Wireless Power Transfer.

Conventional approaches for wireless power transfer rely on the mutual coupling (near-field or far-field) between the transmitter and receiver transducers. As a result, the power-transfer efficiency of these approaches scales non-linearly with the cross-sectional area of the transducers and with the relative distance and respective alignment between the transducers. In this paper we show that when the operational power-budget requirements are in the order of microwatts, a self-capacitance (SC) based power delivery has significant advantages in terms of power transfer-efficiency (PTE), receiver form-factor and system scalability when compared to other modes of wireless power transfer (WPT) methods. We present a simple and a tractable equivalent circuit model that can be used to study the effect of different parameters on the SC-based WPT. In this paper we have experimentally verified the validity of the circuit using a cadaver mouse model. We also demonstrate the feasibility of a hybrid telemetry system where the microwatts of power that can be harvested from SC-based WPT approach is used for back-scattering a radio-frequency signal and is used for remote sensing of in-vivo physiological parameters like temperature. The functionality of the hybrid system has also been verified using a cadaver mouse model housed in a cage that was retrofitted with 915 MHz RF back-scattering antennas. We believe that the proposed remote power-delivery and hybrid telemetry approach would be useful in remote activation of wearable devices and in the design of energy-efficient animal cages used for long-term monitoring applications.