Friction-Based Interconnection of Stretchable Liquid Metal-Based Coil with Rigid Capacitors for Mechanically Durable...

Textile-integrated meander coils offer a promising platform for body-scale wireless powering of wearable devices. Liquid metal (LM)-filled stretchable tubes are ideal wiring for these coils given their high stretchability and conductivity. Efficient wireless power transfer requires integrating rigid capacitors into this stretchable wiring. However, conventional rigid-soft interconnections using adhesion-based chemical fixation remain mechanically fragile due to poor adhesion in stretchable materials. To address this, we propose capsule-assisted, friction-based mechanical fixation. Rigid capsule-covered capacitors are inserted into LM-filled tubes and secured via friction. These capsules increase contact area and pressure for robust mechanical fixation during stretching while covering capacitor edges to minimize stress concentration during bending. By experimentally optimizing capsule dimensions, our friction-based interconnection withstood stretching and bending forces of 30.3 ± 0.9 and 25.6 ± 2.0 N, respectively, outperforming conventional adhesive joints by 2.7 and 3.4 times. Applied to a body-scale meander coil as a proof of concept, this interconnection maintained wireless power for multiple light-emitting diode (LED) and sensor devices. The coil demonstrated stable electrical performance, yielding impedance changes of <1.7% after 100 bending cycles and <3.1% after 100 washing cycles. This method enables washable, durable wireless powering textiles to support battery- and wiring-free wearable sensors in everyday clothing.