Near field chipless tag for food quality monitoring

Acidic and basic volatiles are a by-product of the food spoilage process. We demonstrate a near field coupled volatile absorption pH sensor that can be used for wireless food quality monitoring. The sensor is based on a LC resonator whose resonant frequency changes with the concentration of acidic and/or basic volatiles in the sensor's surrounding environment. Tests with acetic acid and ammonium hydroxide sources show that the sensor can detect the presence of acidic and basic volatiles. The wireless sensor is passive and simple in design, making it an inexpensive, battery-less option for remote monitoring of food freshness during its shelf life.