Molybdenum trioxide (MoO3) Capacitive Soil Moisture Microsensor for In-situ Agriculture Applications: Measurement Studies and Temperature Effects

The soil moisture sensor is of utmost importance in agriculture due to issues including water conservation and disease prediction. This work presents the design and development of a molybdenum trioxide (MoO
₃
) based capacitive soil moisture microsensor. The sensor comprises an inter-digitated electrode (IDE) on a silicon wafer and MoO
₃
is drop cast on IDE, which acts as the sensing film. IDE on Si wafer is mounted on the printed circuit board (PCB) and electrical contacts are taken out. During the lab measurements, we observed changes of 153 pF to 400 pF for different soil moisture ranges of 7% to 55% respectively in the black clayey soil. The response time for the fabricated microsensors is around 120 seconds in the soil for all types of measurements. Further, the change in response of the sensor is 16% when the temperature varies from 25 °C to 50 °C. Thus, we conclude that MoO
₃
is one of the potential oxides in the capacitive sensor platform and can be used for the in-situ soil moisture sensing.