The demand for maple syrup is increasing, and producers must improve efficiency to maintain high-quality products at a low cost. To meet transparency, density, color, and aroma standards, quality control systems are established throughout boiling processes. However, microbial growth in the harvesting infrastructure throughout the sugaring season has been a significant challenge, as biofilms reduce sap flow rates or cause clogging of sap lines. Microbial growth also degrades the product's quality by changing the syrup's color, taste, and viscosity. Therefore, smart farming is an essential solution that can bridge the gap between microbial growth monitoring and maple syrup quality. Wireless Sensor Networks in maple forests, also known as sugar bushes, are vital for monitoring processes such as sap harvesting using individual sensor nodes that send current biogeochemical information to a field station. A biofilm sensor is needed to indicate biofilm formation in real time.This presentation introduces a microfabricated electrochemical impedance spectroscopy sensor (EIS) tailored to measure biofilm formation in sap infrastructure during the harvesting season, defined by temperature fluctuations between -10 and 20 ˚C. Impedance spectroscopy sensors were fabricated using standard evaporation, lithography, and wet chemical etching techniques. To increase the sensitivity of biofilm formation, interdigitated electrodes with a 15 µm gap between two electrodes were utilized, and 50 gold electrode pairs were implemented on a borosilicate glass wafer. Diced EIS dies were integrated into an additively manufactured housing that allowed electrochemical measurements in maple sap in the laboratory or sugar bush.To test the efficacy of the EIS sensor, a Pseudomonas Sp. strain was extracted from maple sap harvested in 2023 at the Michigan State University Upper Peninsula Forestry Innovation Center and grown at room temperature. Sterile sap was filled into the flow cell and inoculated with microorganisms after 4 h. All experiments were performed in triplicates, and abiotic controls followed the same procedure minus the injection of cell culture enrichments.Impedance data were captured every 30 minutes for 7 days, and impedance changes to the abiotic signal were characterized at defined frequencies. After 1 hour, an impedance change of 15% was observed. The impedance magnitude decreased over 7 days, indicating biofilm maturation. Biofilm growth on the EIS surface was confirmed with confocal microscopy. An impedance increase was observed in some cases, indicating biofilm detachment. Additionally, a model has been developed that relates the impedance response of maple sap to the required outdoor temperature range of -10 and 20 ˚C. Ultimately, this paper shows EIS as a valuable tool to characterize biofilm formation caused by maple sap.
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