A Bio-mimetic Leaf Wetness Sensor

Leaf wetness duration (LWD) is an important measurement in agricultural meteorology since it is determining factor in pathogen infection and critical to the rate of plant disease development. As a result, agricultural communities have adopted leaf wetness sensors as a part of crop management systems to monitor the duration of leaf wetness resulting from dew, rainfall, or irrigation events. There are several commercially available electronic LWD sensors on the market. Although these systems are robust and highly precise, they are unable to fully mimic the surface properties and wettability of real leaves. As a result, accurately measuring LWD to estimate the risk of fungal disease is challenging. To mitigate the limitations of commercially available leaf wetness sensors (LWS) we have fabricated an interdigital capacitive sensor insulated with a bio-mimetic polydimethylsiloxane (PDMS) surface. Through a multi-step molding process, we were able to replicate the complex surface topography of leaves and integrate it into a capacitive wetness sensor. There was up to a 60% discrepancy in how long it takes for the LWS to reach full water surface saturation between leaf replica LWS and the commercial LWS, reflecting a more wettable leaf surface compared to that of the commercial sensor. These results verify the importance of incorporating leaf wettability in LWD measurement while also offering a simple fabrication method in producing a more accurate LWS.