Environmentally friendlier wireless energy power systems: The coil on a paper approach

Paper is ubiquitous in everyday life and a low-cost environmentally friendly material. Thus, the printing of advanced conductive/magnetic nanomaterials on paper will allow the scalable production of flexible smart electronics, including energy-storage devices, sensors, inductors or antennas, among others, contributing towards more sustainable electronics. Particularly, wireless charging technologies are becoming essential for internet-ofthings (IoT)-related electronic devices due to the ever-decreasing dimensions of portable/mobile devices that limit the quantity of energy that can be stored. Here, screen-printed paper-based coils and inductors operating on the 1-20 MHz range are presented based on Poly(vynil alcohol)/Fe3O4 and Ag inks. The ability of the printed cores and inductors to be incorporated on flexible wireless power transfer modules (WPTM) is technologically demonstrated by wireless powering light-emitting diodes (LEDs). The achieved induction efficiency of 94% is the highest reported on printed and flexible WPTM. The printed coils are also characterized by mechanical, hydrophobic and electrical properties that are suitable for IoT and industry 4.0 applications.