Screen Printed, Flexible, Capacitive Soil Moisture Sensor Compatible with High Frequency Electronics

Soil moisture is a key factor in soil processes and plant health. Current soil moisture sensors are either expensive and bulky, such as time domain reflectometry (TDR) sensors, or inexpensive and unreliable, such as resistive sensors. These limitations prevent soil moisture sensors from being deployed in the high density required for precision agriculture and smart farming. Capacitive soil moisture sensors provide a good balance of accurate measurements and at low cost, but if they are read at a low frequency their measurements can be affected by soil ion concentration. We present a screen printed, flexible capacitive soil moisture sensor which can overcome these limitations through parallel design of the sensor and readout electronics. Screen printed devices can be easily scaled up to roll-to-roll manufacturing, drastically reducing the device cost. Additionally, the flexibility of the sensors allows them to be easily installed with other devices. We demonstrate a sensor design compatible with high frequency, low cost electronics which are currently in development.