Metamaterial-Inspired Microwave Sensor for Ethanol Detection

In this work, a high-sensitive microwave sensor based on an improved split ring resonator (SRR) for detecting ethanol concentration in aqueous ethanol solutions is proposed. This biosensor combines SRR with the inter-digital capacitor (IDC) and adds two pairs of IDCs on the resonator for enhanced electric field concentration over a larger surface area, which provides higher sensitivity for testing dielectric liquids. The coupling between the two resonant elements and the transmission line deepens the amplitude of the biosensor. The material under test (MUT) is properly placed in the IDC region of the SRR, where the highest electric field strength can achieve low-cost, pollution-free, non-contact, high-sensitivity detection. This sensor resonates at3.44GHz with a resonance amplitude of -17dB. Ethanol in the concentration range of 20%-100% can be measured by the resonant frequency and the S 21 parameter’s change. The sensitivity of this microwave sensor for measuring ethanol is 0.75 MHz/% and 0.03 dB/%, which can be used for quantitative detection of ethanol solution.