Fully-Inkjet-Printed Ag-Coil/NiZn-Ferrite for Flexible Wireless Power Transfer Module: Rigid Sintered Ceramic Body into Flexible Form

Despite the material performances being superior to those of organic materials, inorganic materials are typically excluded for use in flexible and deformable electronic systems because of their rigid nature and the requirement for high processing temperature. This work presents a novel method of utilizing rigid NiZn-ferrite films in a flexible platform and offers an opportunity to realize a flexible wireless power transfer (WPT) module. Inkjet printing is introduced in this study since it can coat NiZn-ferrite films as well as pattern inductor coils for WPTs. A thermochemically inert buffer layer is selected based on a thermodynamic analysis and is introduced as a buffer layer for the NiZn-ferrite to prevent chemical reaction between the ferrite film and the substrate and ensure that the ferrite film can be easily separated from the substrate during a high-temperature sintering process. A Ag-inductor coil is printed on the NiZn-ferrite layer, and then the entire layer is embedded into polydimethylsiloxane, which renders the WPT module flexible. The flexibility of the WPT module is characterized by a bending test, and the structural and magnetic properties are also investigated. The performance of the flexible WPT module is demonstrated by transmitting wireless power to a light emitting diode.