Specific Detection of Organic and Inorganic Solution Based on Microwave Resonator Array

Real-time measurement and identification of solutions are necessary for many areas such as biomedicine, food, and pipeline etc. This study presents a microwave sensor array combing with principal component analysis (PCA) to identify the different solutions and detect their concentration severally, as well as in their mixed state as a mediator-free method for specific detection. First, as the representative samples, ethanol and potassium chloride (KCl) solutions in different solutions are prepared and detected by the different resonances of the array units. In addition, the selectivity is realized via the multiple detected parameters under PCA. With the increased resonant frequency from 3 GHz to 6 GHz, the sensitivity of ethanol solution (indicated by frequency shift) increases from 0.3 MHz/% to 0.93 MHz/%. The concentration of the individual substances in mixed solutions of ethanol and KCl is also tested, demonstrating that the resonance of 3.41 GHz and 4.02 GHz can effectively detect KCl’s concentration, while the 5.46 GHz can be utilized to detect ethanol.