A Novel Microstrip Sensor Based on Closed Loop Antenna for Adulteration Detection of Liquid Samples

The design, development, and analysis of a planar microstrip sensor operating at 2.4 GHz for the detection of adulteration in liquid samples is presented. The sensor characterizes the samples based on the material properties which in turn affects the electric field fringing from the sensing area. In particular, a closed loop microstrip antenna is developed and used for the sensing application. The sensor is designed and analyzed using simulation software and the fabricated prototype is experimentally validated. Parametric analysis of the design variables and mathematical modeling of the sensor operations are carried out by analyzing the fields generated within the sensor. A case study for adulteration testing is carried out by choosing milk as the sample. Qualitative and quantitative testing using the milk as sample has been carried out experimentally under different test conditions. For quantitative testing, water is added to milk as the adulterant and for qualitative testing, usual chemical adulterants that are mixed with milk are added and the variations in operating frequency and return loss are analyzed. From the analysis, it could be observed that the shift in the operating frequency and return loss are dependent on the changes in dielectric permittivity of the sample loaded on to the sensor surface. From this analysis, the adulteration rate in milk can be estimated based on the variation in permittivity of the adulterant that is added to the milk. The same procedure can be extended in detecting the adulteration of any liquid samples.