This study presents the design and implementation of a crop environmental monitoring system powered by a plant–soil bioelectrochemical energy source. The system integrates a Cu–Zn electrode power unit, a boost converter, a supercapacitor-based energy management module, and a wireless sensing node for real-time monitoring of environmental parameters. Unlike conventional plant microbial fuel cells (PMFCs), the output current originates partly from the galvanic effect of Cu–Zn electrodes and is further regulated by rhizosphere conditions and microbial activity. Under the optimal external load (900 Ω), the system achieved a maximum output power of 0.477 mW, corresponding to a power density of 0.304 mW·cm⁻². Stability tests showed that with the boost converter and supercapacitor, the system maintained a stable operating voltage sufficient to power the sensing node. Soil moisture strongly influenced performance, with higher water content increasing power by about 35%. Theoretical calculations indicated that Zn corrosion alone would limit the anode lifetime to ~66 days; however, stable output during the experimental period suggests contributions from plant–microbe interactions. Overall, this work demonstrates a feasible self-powered crop monitoring system and provides new evidence for the potential of plant–soil bioelectrochemical power sources in low-power applications.

Liquid-nitrogen biobanks require stable and spatially uniform vapor-phase temperatures for long-term biological-sample storage. Transient computational fluid dynamics models were developed for automated and non-automated configurations under empty-, half-, and full-load conditions. Loading was represented using different porosity settings for homogenized storage regions, and transient temperature evolution and monitoring-point temperature uniformity were evaluated. In the automated biobank, the final monitoring-point average temperature increased from −187.90 °C under an empty load to −183.21 °C under a full load, while the final monitoring-point temperature difference increased from 10.67 °C to 13.70 °C. In the non-automated biobank, the corresponding average temperature increased from −169.65 °C to −165.38 °C, and the temperature difference increased from 7.81 °C to 10.25 °C. In both configurations, the warmest monitoring locations were more responsive to loading than the coldest locations, indicating increased spatial non-uniformity. Under their respective modeled conditions, the automated configuration reached lower monitoring-point average temperatures but exhibited larger temperature differences, whereas the non-automated configuration showed higher average temperatures but smaller differences. Because the models differed in scale, internal arrangement, thermal boundaries, and monitoring layout, the cross-configuration comparison is descriptive rather than normalized. The results provide a model-based basis for structural screening, loading management, and functional temperature-monitoring strategies.

Liquid-nitrogen biobanks need temporary, spatially distributed temperature records, but conventional batteries and radios become unreliable far below their rated operating temperatures. We developed a finite-duration wireless logging system that separates sensing and communication in both space and time. A remote PT1000 probe follows the cryogenic environment, whereas a polytetrafluoroethylene (PTFE)/aerogel enclosure delays cooling of the battery and electronics; data are stored locally during exposure and retrieved by Bluetooth Low Energy only after warm-up. This differentiated thermal-path and staged-communication architecture is the principal novelty of this work. A transient node model reproduced the internal cooling trend, with a mean absolute error (MAE) of 3.74 °C, a root mean square error (RMSE) of 3.92 °C, and r = 0.9986, with a 123.5 s difference in the time to reach −50 °C. Nine nodes logged for 38.4–47.2 min (mean 44.2 min), and all reconnected after 35 min of warm-up at approximately 25 °C. In a one-node indoor engineering test, historical records were recovered without packet loss over 2–10 m, and 18 locations in an operating biobank yielded retrievable temperature histories. The system therefore supports short, non-real-time mapping and workflow assessment; it is not a substitute for fixed real-time alarm or metrological monitoring systems.