A Liquid Sensor Based on Frequency Selective Surfaces

A novel, simple and easy-to-fabricate liquid sensor using frequency-selective surfaces (FSSs) is proposed. The new concept based on modifying the capacitance between adjacent FSS elements when materials of different electrical characteristics are inserted. change in produces a resonant frequency. design consists 9 $\times $ array square loops notation="LaTeX">$0.31\lambda \times 0.31\lambda unit cells with trenches loops. filled liquids under test (LTUs). structure operates at 4.6 GHz without any liquid. When inserted trenches, resonance frequency varies relation to dielectric constant This observed by measuring transmission coefficient ( notation="LaTeX">$S_{21}$ ). Butan-1-ol, ethanol, methanol, propan-2-ol, xylene used demonstrate sensing function. maximum sensitivity 8.65% for was achieved. Furthermore, very low differences were measured expected loss tangent, thus validating design. device inexpensive, compact, easy make scalable large-area operations detection microwave applications. technique has potential applications reconfigurable FSS.