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The conventional rigid and energy-limited battery-powered wireless sensor network (WSN) needs to be improved for continuously sensing temperature and guaranteeing food quality and safety in cold storage. This paper aims to propose and develop a light-energy-harvested flexible wireless temperature-sensing patch (LTSP) for food cold storage. The LTSP could provide sustainable light-energy-powered battery-free applications in low-light conditions. The flexible circuit of LTSP was fabricated by the photosensitive etching method with a polyimide (PI) film as the flexible substrate and copper (Cu) as the circuit. The light energy was harvested by two pieces of amorphous silicon solar cells and stored in a micro-supercapacitor by the power-management module. The LTSP is flexible and can be bent. The micro-supercapacitor of 1 mF was rapidly charged from 0 to 3 V after only about 47 s and the micro-supercapacitor of 10 mF took about 465 s under the light intensity of 2100 lux by the light-energy-harvesting module. The temperature of the packaged food was sensed and acquired by a wireless module. The temperature-sensing data and voltage status of the micro-supercapacitor could be displayed on a liquid crystal display (LCD) in real time or read by radiofrequency identification (RFID) or near-field communication (NFC) reader such as NFC-enabled smart phone or device via a frequency of 13.56 MHz. The LTSP worked well under a light intensity of 2100 lux. The temperature fluctuation could be acquired under the table grapes storage temperature of 0 °C. The proposed LTSP has potential applications in food cold storage in supermarkets with light-energy reuse and could provide insights into the development of sustainable food quality and safety.

Waterless transportation for live grouper is a novel mode of transport that not only saves money, but also lowers wastewater pollution. Technical obstacles remain, however, in achieving intelligent monitoring and a greater survival rate. During live grouper waterless transportation, the stress response is a key indicator that affects the survival life-span of the grouper. Studies based on breathing rate analysis have demonstrated that among many stress response parameters, breathing rate is the most direct parameter to reflect the intensity. Conventional measurement methods, which set up sensors on the gills of groupers, interfere with the normal breathing of living aquatic products and are complex in system design. We designed a new breathing monitoring system based on a completely non-destructive approach. The system allows the real-time monitoring of living aquatic products’ breathing rate by simply placing the millimeter wave radar on the inner wall of the incubator and facing the gills. The system we developed can detect more parameters in the future, and can replace the existing system to simplify the study of stress responses.

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