Fig. 5: Wireless power transfer efficiency of stretchable spiral coils.
a Two-port network model analysis based on magnetic resonant coupling mode. Scattering parameters S11 and S21 and efficiency η (b–d) between primary coil and stretchable coil at different vertical distances. Insets: photographs of coupling of two coils under testing (c); induced voltage of two coils with different vertical distances at 10 MHz (d). e Efficiency η between primary coil and stretchable coils with different numbers of turns. Insets: induced voltage shown in e at 10 MHz. f Efficiency η between primary coil and stretchable coils with tensile strain. Insets: induced voltage measured from stretchable coils with a tensile strain of 50% at different frequencies (left); efficiency η and resistance RS versus tensile strain at 10 MHz (right).
