VOLUME FRACTION EXTRACTION FOR BINARY MIXTURE OF ETHANOL AND METHANOL USING OPTIMIZED MICROWAVE MICROFLUIDIC SENSOR

An optimized microfluidic sensor for extracting volume ratio of binary mixture comprising of ethanol and methanol using electrical resonance technique has been presented in this work. In order to detect small changes in composition of binary mixture, a split-ring resonator structure with enhanced sensitivity was designed to operate around 2.5 GHz. A resonator was designed using HFSS, which possessed enhanced sensitivity. A novel algorithm for optimization was devised for binary mixture of the two liquids. The resonator was fabricated and tested for validation of results. Samples of ethanol and methanol mixture in different volume ratios were prepared and filled in micro-capillary tubes. These tubes were placed inside the resonant structure to perturb electric field. Variations in resonant properties due to change in volume ratio of liquid mixtures were analyzed. Resonant frequency, s-parameters, and quality factor of structure were measured. It was observed that change in volume fraction as small as 1/100 resulted a shift of 0.25 MHz in resonant frequency (relatively high level of sensitivity). Measured results were utilized by mathematical model to compute volume fraction of liquid in these mixtures.