Transparent and Flexible Antenna With Polarization Reconfigurability Using EGaIn for Wearable Applications

A visually unobtrusive and flexible antenna with polarization reconfigurability is investigated for wearable devices. Optically transparent elastomer is adopted to form the substrate, and the conductor of single-layer coplanar waveguide (CPW)-fed slot antenna is translucent conductive mesh fabric. Liquid metal (LM) EGaIn is employed as perturbative branches, implementing circularly polarized radiation while maintaining flexibility. By controlling the position of LM, three operating states are reconstructed, including left-/right-handed circular polarizations (CP) both in the 2.45- and 5.8-GHz industrial, scientific, and medical (ISM) bands and linear polarizations (LPs) in 3.5-GHz 5G n78 band (3.3–3.8 GHz) and 5.8-GHz ISM band. The compliance of the proposed antenna with radiation safety standards is confirmed by numerical results. A prototype of the proposed antenna with channels was fabricated and measured, wherein the switching between three states was realized by physically controlling the flow of LM within the channels through pumps. Finally, visual unobtrusiveness of the antenna was verified experimentally, where the proposed antenna has optically 89.8% transmittance in 41% of the area and 43% transmittance in 55% of the area.