電池容量の小さなウェアラブル機器は長期の使用が難しく機能に制限があった。布型無線給電器により、使用中のウェアラブル機器を給電する場合、人体の電磁界暴露を抑えるため送電電力を制限する必要があるほか、導電糸の損失が大きいことから給電効率が低くなる。そこで、電磁界暴露を抑制しつつ高い効率で体表付近のデバイスへ給電するために、従来我々が通信用に開発したメアンダコイルを改善した。柔軟な液体金属製のワイヤーを用いることで、約40%の効率で2.5Wの電力を給電できる安全で高効率なシステムを実現した。

Wearable devices with small battery capacity are difficult to use for long time and have limited functions. Although a cloth-type wireless charger has the potential to stably power up functional wearable devices in the use, the electromagnetic field exposure in the body limits the power transmission amount, and the high loss of conductive yarns results in low power transfer efficiency. Therefore, we first improved a meander coil that we previously developed for wireless communication to efficiently power up the devices near the body surface while suppressing electromagnetic field exposure. Then, by using flexible liquid metal wires, we realized a safe and efficient wireless charging system capable of supplying 2.5 W of power with an efficiency of about 40%.

R. Takahashi, W. Yukita, T. Yokota, T. Someya, and Y. Kawahara, “Meander Coil++: A Body-scale Wireless Power Transmission using Safe-to-body and Energy-efficient Transmitter Coil,” Proceedings of the 2022 CHI Conference on Human Factors in Computing Systems (ACM CHI’22), Article No.: 390, Pages 1-12, New Orleans, LA, USA, April 2022 (Best Paper Award). https://doi.org/10.1145/3491102.3502119

Contact: takahashi@akg.t.u-tokyo.ac.jp