Flexible rectifying metasurfaces for efficient wireless energy harvesting

Abstract A highly efficient, ultra-thin, and flexible rectifying metasurface (RMS) operating at 5.8 GHz is presented. The unit cell utilizes a composite symmetric structure. This structure consists of a double-cross and a notched rectangular ring. This geometric symmetry ensures polarization insensitivity. Structural parameters were optimized to achieve simultaneous impedance matching. The metasurface matches the impedance of free space ( Z 0 ) and provides a conjugate match to the diodes. This eliminates the need for external matching networks, thereby significantly enhancing system integration. Furthermore, the high-Q chip inductors within the interconnect units serve both as direct current (DC) pathways and, in conjunction with the unit’s inherent parasitic capacitance, form radio frequency (RF) filters. This coplanar integration obviates the need for a separate power combining network. A 6×6 array (96 mm × 96 mm) was fabricated on a 0.6 mm thick polyimide substrate. Experimental measurements demonstrate a total efficiency exceeding 67% across all polarization angles. The efficiency remains above 64.2% within an incident angle range of 0° to 30°. Additionally, the system maintains an efficiency of 66.74% when bent to a curvature radius of 180 mm. These results demonstrate excellent conformability. These attributes make the proposed RMS a highly efficient and compact solution for wireless power delivery, particularly for Internet of Things (IoT) and wearable applications.