Friction jointing of distributed rigid capacitors to stretchable liquid metal coil for full-body wireless charging clothing

For full-body wireless power transfer (WPT), a liquid metal (LM)-based meandered textile coil has been proposed. Multiple rigid capacitors must be inserted in a long coil for efficiency; however, the conventional adhesive jointing suffers from the fragile connection between a rubber tube filled with LM and the capacitor due to the poor adhesion of the rubbers. This paper presents a friction-based jointing, which covers the capacitor with a rigid capsule to enhance the frictional force between the tube and capsule. By experimentally optimizing the capsule design, the LM coil with capacitors showed 3.1 times higher stretch tolerance (31.8 N) and 3.5 times higher bending tolerance (25.9 N) than the adhesive jointing. Moreover, the WPT garment prototype shows excellent mechanical durability against repeated stretching and washing over 100 times. Our full-body meandered textile coil can enable wireless charging to wearable devices around the body for long-term continuous healthcare monitoring, activity recognition, and AR/VR.