A multiband, polarization-controlled energy harvesting metasurface is presented in this article for harvesting electromagnetic energy in the Wi-Fi bands. Inspired by the split-ring resonator (SRR), a metasurface of SRRs is designed by nesting multiple SRRs together. The novelty of the design lies in the controllable multiband polarization and adjustable absorption frequency, so as to achieve the active modulation of energy harvesting on the metasurface at different frequencies. The metasurface is composed of a periodic array of SRRs unit cells, an impedance-matched rectifier, and a load. Metasurface arrays and rectifier integration are proposed to reduce power losses, while the channels formed by the array enhance energy density and improve the ability to capture energy. Moreover, the design for the rectifier is capable of rectifying RF energy from multiple Wi-Fi bands simultaneously at low input RF power density. The finite array of $5\times $ 5 SRRs absorber is fabricated and tested. Measurements in an anechoic chamber show that the fabricated prototype reaches the efficiency of 66.5% at 2.4 GHz, 40.6% at 5.2 GHz, 35.6% at 5.8 GHz under transverse electric (TE) polarization, and 38.3% at 5.3 GHz under transverse magnetic (TM) polarization when the incident power density is greater than 66 $\mu \text{W}$ /cm ² .

Flexible pressure sensors are essential components of electronic skins for future attractive applications ranging from human healthcare monitoring to biomedical diagnostics, robotic skins, and prosthetic limbs. Here we report a new kind of flexible pressure sensor. The sensors are capacitive, and composed of two Ag wrinkled electrodes separated by a carbon nanotubes (CNTs)/polydimethylsiloxane (PDMS) composite deformable dielectric layer. Ag wrinkled electrodes were formed by vacuum deposition on top of pre-strained and relaxed PDMS substrates which were treated using an O₂ plasma, a surface functionalization process, and a magnetron sputtering process. Ultimately, the developed sensor exhibits a maximum sensitivity of 19.80% kPa⁻¹ to capacitance, great durability over 500 cycles, and rapid mechanical responses (<200 ms). We also demonstrate that our sensor can be used to effectively detect the location and distribution of finger pressure.