A Novel Method For Battery-free Food Monitoring Powered by NFC-based Energy Harvesting

Abstract

In this thesis, the author presents a novel approach for battery-free food freshness monitoring to track the freshness of different sorts of food such as pork, chicken, and fish during storage. The system includes a smart sensor tag mounted inside a food container, and an NFC-enabled smartphone playing as a reader. The proposed method employs the gradual increase of air pressure caused by the gas emission during storing in order to eliminate the disadvantages of typical monitoring systems. Additionally, we aim to design a smart sensor tag that is able to operate passively without an external power source. Toward this end, Near Field Communication (NFC)-based energy harvesting is utilized in this thesis to accomplish the self-powered operation. To demonstrate the feasibility of the proposed method, a set of experiments with the abovementioned food are deployed at two different storing environments. In each experiment, 200g of the food is placed in a 2-liter container integrated with the smart sensor tag. The air pressure inside the container is collected as an indicator of food freshness by a sensitive pressure sensor. The experimental results show a significant rise in air pressure which is able to be detected at high accuracy. With this proposed method, the smart sensor tag achieves the smallest size in this field (2.5cmx2.5cm) and is capable of working at ultra-low power consumption, less than 1mW, compared with other ordinary approaches whose power consumption normally surpass 10mW. Besides, pressure values are used to classify food freshness into different levels displayed on a developed mobile application.