A Wearable All-Printed Textile-Based 6.78 MHz 15 W-Output Wireless Power Transfer System and its Screen-Printed Joule Heater Application

While research in passive flexible circuits for Wireless Power Transfer (WPT) such as coils and resonators continues to advance, limitations in their power handling and low efficiency have hindered the realization of efficient all-printed high-power wearable WPT receivers. Here, we propose a screen-printed textile-based 6.78 MHz resonant inductive WPT system using planar inductors with concealed metal-insulator-metal (MIM) tuning capacitors. A printed voltage doubler rectifier based on Silicon Carbide (SiC) diodes is designed and integrated with the coils, showing a power conversion efficiency of 80-90% for inputs between 2 and 40 W. Compared to prior wearable WPT receivers, it offers an order of magnitude improvement in power handling along with higher efficiency (approaching 60%), while using all-printed passives and a compact rectifier. The coils exhibit a simulated Specific Absorption Rate (SAR) under 0.4 W/kg for 25 W received power, and under 21◦C increase in the coils’ temperature for a 15 W DC output. We finally demonstrate a wirelessly-powered textilebased carbon-silver Joule heater, capable of reaching up to 60◦C at 2 cm separation from the transmitter, as a potential wearable application which can only be wireless-powered using the proposed system.