Flexible and wireless 'stick-and-detect' sensor node based on laser-induced graphene for real-time temperature monitoring toward cold chain applications

초록

Robust temperature monitoring is fundamental to cold chain logistics for vaccines, biopharmaceuticals, and food. However, existing approaches often rely on rigid sensors that cannot directly measure product temperature and offer limited remote sensing capabilities. Here, we report a flexible, wireless "stick-and-detect" sensor node based on a laser-induced graphene (LIG) temperature sensor mounted on a flexible printed circuit board (FPCB), enabling real-time and remote monitoring by conformally adhering to irregular surfaces. The fabrication parameters for the LIG electrode are optimized, and a facile mechanical pressing is introduced to improve deviceto-device uniformity, essential for scale-up and potential commercialization. Specifically, the initial resistance becomes significantly uniform, with a 96% reduction in standard deviation among LIG sensors after pressing. The LIG sensor integrated with the FPCB serves as the sensor node and reliably monitors deep-freeze temperatures from -30 degrees C to 10 degrees C. Powered by wireless inductive coupling, the nodes construct the wireless sensor network (WSN) and can be complemented by a GPS node for tracking cold chain logistics. We validate sensing fidelity and communication robustness across proof-of-concept scenarios: (i) dual-region monitoring within a single chamber; (ii) remote monitoring across two physically separated chambers; and (iii) door-open incident detection in a chamber, where a door-mounted node captures a rapid temperature rise, triggers a dashboard alert, and confirms recovery after closure. The developed sensor platform provides reliable and traceable temperature monitoring, potentially facilitating cold chain monitoring to preserve the integrity of temperature-sensitive products.

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