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An X-band, free-space microwave sensor consisting of 30 radial spokes connected in a central hub with a gap region was designed, fabricated and tested. The sensor structure results in an electric dipole at 10 GHz with a split circular disc capacitor at the center. Viruses, dust, and soot particles in the gap region change the sensor’s impedance and its reflection coefficient monitored by a horn antenna and a network analyzer. The sensor sensitivity was 85. 02 MHz/microliter for deionized water, 89. 5 MHz/microliter for uninfected saliva, and 94. 6 MHz/microliter for SARS-COV-2 infected saliva with 10 3 viruses/ L. Its sensitivity to a dielectric sample (5. 84) was 3. 23 MHz/mm 3, and for iron particles was 16. 25 MHz/mm 3. All these samples were smaller than /30 at 10 GHz and could not be detected on uniform dielectric or metallic substrates without the spoke structure. A 2 2 array of spoke sensors was also constructed and tested as a feasibility study for designing larger metamaterial (MTM) periodic arrays.
Tabib‐Azar et al. (Fri,) studied this question.