A Hybrid Magnetoelastic Wireless Sensor for Detection of Food Adulteration

This paper investigates a step by step design procedure of a hybrid passive wireless sensor. The hybrid sensor measures both the electrical (dielectric constant) and the mechanical (viscosity) properties of liquid, providing a two-factor quality control. The hybrid sensor is based on an inductor-capacitor resonant tank coupled with a magnetoelastic strip. The mechanical and the electrical resonances change as a function of viscosity and dielectric constant, respectively. Two different hybrid sensor designs are investigated: 1) a parallel plate capacitor coupled with a separate amorphous ferromagnetic magnetoelastic strip (Metglas) and 2) a capacitor made using two parallel mounted magnetoelastic strips. The sensors are integrated as part of the 'smart vial' making it field operable for food quality monitoring and control. Here, detection of adulteration in extra virgin olive oil is achieved by measuring the change in viscosity and dielectric constant for different adulteration levels. The real part of the dielectric constant for different liquid samples is measured in the frequency range of 3-24 MHz. The hybrid sensor is able to detect adulteration levels below 10% in volume. These sensors can be integrated with passive RFIDs for simultaneous measurement of multiple samples in an array format.