Metasurface absorber based on water meta “molecule” for X-band microwave absorption

Two different sizes of water “atoms” embedded in a flexible silicone matrix are combined together to form water “molecules” and used as the resonating elements of the metasurface to achieve wideband microwave absorption. The sizes of the two “atoms” are chosen such that their resonating frequencies couple to give a whole X-band absorption with a bandwidth of –10 dB. The design and simulation of the unit cell are carried out to achieve the desired results with an overall absorber thickness of ∼3.0 mm (i.e., only λ/12 of the lower cut off frequency). A wide absorption bandwidth of 4.2 GHz with an absorption efficiency of 90% is observed for the fabricated metasurface absorber in an X-band waveguide environment. The evaporation of water is prevented by embedding the water “molecules” in a silicone substrate, and its flexibility helps in retaining the designed shape. The arrayed structure of the water “molecules” provides the required effective permittivity and permeability of the metasurface by generating Mie resonance. Numerical investigation shows the polarization insensitive absorbance of the symmetrical unit cell structure and wide-angle absorption performance of the absorber for both transverse magnetic and electric modes.