Recent advancements in the semiconductor integrated circuits and functional materials technologies have accelerated the demand of electronic and biomedical devices such as internet of things (IoT) and wearable sensors, which have low power consumption, miniature size and high data transfer efficiency. Wireless power transfer (WPT) has become the alternative solution to current electronic devices that rely on bulky batteries to supply the power and energy. Near Field Communication (NFC) technology is extensively used for wireless power transfer, where devices communicate through inductive coupling via induced magnetic fields between transmit and receive coils (loop antennas). Thin NFC sheets made of soft magnetic materials are inserted between antennas and metal case of wireless gadgets, such as mobile phones or tablets, to reduce the degradation of antenna gain and radiation efficiency due to generation of eddy currents. To enhance the efficiency of wireless power transfer, magnetic materials with superb properties such as high permeability, low magnetic loss and high resistivity are highly desirable. In this chapter, we will provide an overview of the current state of the art, recent progress and future directions in NFC based wireless power transfer, with the special focus on near field communications operating at 13.56 MHz.
Part of the book: Wireless Power Transfer
The size and shape dependent tunable electromagnetic (EM) properties of magnetite – Fe3O4 nanoparticles makes them an attractive material for various future electronics and biomedical device applications such as tunable attenuators, miniaturized isolators and circulators, RF antennas, EM shielding, and biomedical implants etc. The strategic design of RF devices requires specific dielectric and magnetic properties according to the applications, which in turn depends on the size and shape of the particles. At nanoscale, iron oxide’s magnetic and dielectric properties are very different from its bulk properties and can be tuned and enhanced by utilizing different synthesis approaches. In this chapter, we summarize electromagnetic properties of magnetite (Fe3O4) nanomaterials such as, complex permeability, complex permittivity, magnetic and dielectric loss tangents, saturation magnetization, temperature dependence, and ferromagnetic resonance; and how these properties can be optimized by varying different synthesis parameters. Finally, Fe3O4 nanocomposites will be explored by using different synthesis approaches for implementation of RF and microwave applications and we will conclude the chapter with future recommendations.
Part of the book: Iron Oxide Nanoparticles