Converting a plant to a battery and wireless sensor with scatter radio and ultra-low cost

Electric potential (EP) signals are produced in plants through intracellular processes, in response to external stimuli (e.g., watering, mechanical stress, light, and acquisition of nutrients). However, wireless transmission of a massive amount of biologic EP signals (from one or multiple plants) is hindered by existing battery-operated wireless technology and increased associated monetary cost. In this paper, a self-powered batteryless EP wireless sensor is presented that harvests near-maximum energy from the plant itself and transmits the EP signal tens of meters away with a single switch, based on inherently low-cost and low-power bistatic scatter radio principles. The experimental results confirm the ability of the proposed wireless plant sensor to achieve a fully autonomous operation by harvesting the energy generated by the plant itself. In addition, EP signals experimentally acquired by the proposed wireless sensor from multiple plants have been processed using nonnegative matrix factorization, demonstrating a strong correlation with environmental light irradiation intensity and plant watering. The proposed low-cost batteryless plant-as-sensor-and-battery instrumentation approach is a first but solid step toward large-scale electrophysiology studies of important socioeconomic impact in ecology, plant biology, and precision agriculture.