A wearable microgrid that centralizes and distributes harvested energy across different body regions can optimize power utilization and reduce overall battery weight. This setup underscores the importance of developing cable-free wireless power transfer (WPT) systems for mobile and portable devices to eliminate the risks posed by wired connections, especially in dynamic and hazardous environments. We introduce a thin, stretchable, and safe hand band capable of watt-level wireless charging through the widely adopted Qi protocol operating at 130 kHz. The implementation of non-adhesive fabric encapsulation serves to protect the 50-μm-thin spiral copper antenna from mechanical strain, ensuring an overall hand band stretchability of 50%. We also create a stretchable “Ferrofabric”, characterized by a magnetic permeability of 11.3 and a tensile modulus of 75.3 kPa, that provides magnetic shielding for the antenna without compromising wearability. The “Ferrofabric” improves the coil inductance but induces core loss in AC application. By fully understanding and managing loss mechanisms such as the skin effect, proximity effect, core loss, and joule heating, we achieve a wireless charging efficiency of 71% and power delivery of 3.81 W in the kHz frequency range. Our WPT hand band is unobstructive to hand motion and can charge a handheld smartphone as fast as a desktop charger or power a battery-free chest-laminated e-tattoo sensor, with well-managed thermal and electromagnetic safety. Through a holistic electromagnetic, structural, and thermal design, our device culminates in a safe, rugged, and versatile solution for wearable WPT systems.

可穿戴微电网将收集的能量集中并分配到不同的身体区域，可以优化电力利用率并减轻电池的整体重量。这种设置强调了为移动和便携式设备开发无线无线电力传输 （WPT） 系统的重要性，以消除有线连接带来的风险，尤其是在动态和危险环境中。我们推出了一种薄而可拉伸且安全的手带，能够通过广泛采用的 Qi 协议进行瓦特级无线充电，工作频率为 130 kHz。非粘性织物封装的实施有助于保护 50 μm 薄的螺旋铜天线免受机械应力的影响，确保整体手带拉伸能力为 50%。我们还创造了一种可拉伸的“铁织物”，其特点是磁导率为 11.3，拉伸模量为 75.3 kPa，可在不影响耐磨性的情况下为天线提供磁屏蔽。“Ferrofabric” 提高了线圈电感，但在交流应用中会引起磁芯损耗。通过充分了解和管理趋肤效应、邻近效应、磁芯损耗和焦耳热等损耗机制，我们在 kHz 频率范围内实现了 71% 的无线充电效率和 3.81 W 的功率输出。我们的 WPT 手环对手部运动无阻碍，可以像桌面充电器一样快速为手持智能手机充电，或为无电池的胸部层压电子纹身传感器供电，并具有管理良好的热和电磁安全性。通过整体电磁、结构和热设计，我们的设备最终为可穿戴 WPT 系统提供了安全、坚固且多功能的解决方案。