Fabrication Techniques for Manufacturing Flexible Coils on Textiles for Inductive Power Transfer

This paper presents a comprehensive evaluation of fabrication techniques for the integration of coils into textiles, for the purpose of enabling low-power wireless power transfer; for example, the powering of on-body monitoring devices, such as heart-rate monitors. Key electrical parameters of the coils required to maximize power transfer efficiency are identified from theory. Flexible coils have been fabricated using standard processes widely used in the textile industry, such as screen printing and embroidery. The screen printed coils were fabricated with a silver-polymer ink on a printed interface layer; the embroidered coils were fabricated using a variety of conductive threads formed by coating textile fibers and through the use of copper fibers. These coils have been experimentally characterized and evaluated for use in wireless power transfer applications. The effects of coil geometry and separation on the dc–dc power transfer efficiency using Qi standard compliant driver and receiver circuits are reported.