Laser‐Induced Graphene‐Based Resistive Leaf Wetness Sensors for Pesticide Spray Deposition

Monitoring pesticide spray deposition across crop canopies requires low‐cost sensors capable of quantifying deposition through leaf wetness, yet carbon‐based resistive leaf wetness sensors (LWS) have not been benchmarked against commercial systems. Here, we demonstrate a scalable resistive laser‐induced graphene (LIG) LWS patterned as an interdigitated electrode for pesticide spray monitoring. The sensor achieved normalized wetness values of 0.15, 1.79, and 2.66% cm −2 after 1, 2, and 5 s of spraying, compared with 0.18, 1.26, and 1.91% cm −2 for a commercial Onset LWS, indicating greater sensitivity at longer exposures. Calibration followed a formulation‐dependent power‐law relationship between resistance and deposited volume. Across three independently fabricated sensors, the selected double‐lased 0.7 mm IDE produced a reproducible tap‐water calibration, with A = 45.167 ± 1.841, n = −0.957 ± 0.021, and R 2 = 0.9921. Short‐term stability depended on solution and environment, with tap‐water calibration changing only 1.5% under greenhouse conditions and 6.3% outdoors after three days, while pesticide formulations exhibited greater drift. Repeated pesticide exposure also caused formulation‐dependent drift, indicating that formulation‐specific calibration and deployment protocols are required. Overall, the low‐cost, scalable LIG LWS offers a promising platform for distributed pesticide spray monitoring and precision agriculture.