The digest presents a methodology to design high-power density multi-MHz capacitive wireless power transfer (WPT) system for wirelessly charging mobile robots while reducing the fringing electric fields within safety limits by using metasurface-based capacitive couplers (metacouplers). A comprehensive circuit model including all parasitic capacitances in the metacoupler is presented and reduced to a simplified four-capacitance model. Furthermore, the impact of varying metacoupler’s physical parameters on fringing fields are studied and an optimized metacoupler design achieving 4.5x reduction in fringing electric fields as compared to conventional couplers is presented. Two 6.78-MHz 3-cm air-gap 1.5-kW capacitive WPT systems, one using a conventional coupler and the other using the proposed metacoupler are designed and built to validate the proposed design methodology. The developed prototype utilizing conventional couplers is powered to 1.5-kW and achieves a power transfer density of 75 kW/m2.
