Collaborative Research: SitS: Collaborative: Long Range Wirelessly Powered Multi-variable Sensor Network for Continuous Monitoring of the Soil Health

This award was made through the "Signals in the Soil (SitS)" solicitation, a collaborative partnership between the National Science Foundation and the United States Department of Agriculture National Institute of Food and Agriculture (USDA NIFA). An urgent need exists for developing inexpensive, long-term deployable sensors that can monitor variable soil conditions in real-time. Understanding the parameters that control the soil health is extremely important in managing the growth and productivity of plants as well as in maintaining soil health. One of the biggest issues associated with new sensors is delivering the power needed to operate the sensors, especially if they are intended to be left buried for long periods of time. This project aims to develop a multi-modal integrated sensor system that can be completely buried 15 cm or deeper in the soil for real-time monitoring of soil gas flows, such as carbon dioxide, ammonia, oxygen, and nitrous oxide, that gives information about soil and plant health. All the electrical power needed for the sensor operation, as well as the signal communication from the sensor, will be delivered using a through-the-soil (TTS) power transmission technique, where electrical energy is sent through the soil, eliminating the need for wires, surface antennas, or embedded batteries. Using TTS power transfer, an agricultural field can be permanently instrumented with sensors without interfering with daily farming operations. Analyzing the collected data will provide key insights related to soil health. This collaborative project involving researchers at Tennessee Technological University, the University of Tennessee Knoxville, and State University of New York at Buffalo will produce new knowledge and engineering techniques that will enhance the abilities of farmers to make better decisions in the growing cycle of crops. This impact alone will reduce waste, improve crop yield, and ultimately generate greater economic income for the Nation and its farmers. The objective of this project is to conduct research toward developing the next-generation of in-situ, networked, multi-modal measurement systems for continuous and uninterrupted monitoring of soil variables over variable space and time periods. Contemporary low-cost soil monitoring systems are discrete and are incapable of detecting soil chemical variables beyond pH. The first project goal is to develop a sensor system that analyzes the vapor phase analytes outgassed during biological processes that characterize soil health. The multi-modal sensor system utilizes three orthogonal physical properties combined into a single platform to detect the analyte vapors with high chemical selectivity and sensitivity in real-time. First and second physical properties use arrays of receptor-immobilized micro-cantilevers to preconcentrate and detect mass changes. The third orthogonal method uses the same arrays to discern the molecular identity of adsorbed gases using photothermal deflection spectroscopy (PDS). These chemically specific, extremely sensitive, and highly compact sensors will be integrated with conventional soil sensing systems that detect moisture, temperature, and pH to create a multi-sensing probe. The second project goal is to power the sensor system using the TTS power transmission technique capable of transferring energy from an electrical power source to a plurality of multi-sensing probes over wide landscape scale areas. The aim is to provide the sensor systems with a stable, uninterruptable source of power to achieve a continuous sensor operation that does not require maintenance and is not susceptible to interferences. The wireless transmission will be accomplished by the excitation of a non-radiating pulsed conduction mode of propagation at radio frequencies. The third project goal is to analyze the data from the wirelessly powered, multi-sensor probe network in order to build predictive algorithms needed to characterize soil health and make critical growing decisions. The research goals of this project will be transformative in broadening understanding of soil health and lead to better environmental practices and enhanced agricultural production. The data and knowledge uncovered during the project will have profound impacts in many areas of science, engineering, and industry. The outcomes of this work include: (1) A historical first in real-time collection of physiochemical specific data in a high spatial and temporal density over a landscape size area and (2) Demonstration of a completely new method of wireless electrical power transmission over a landscape area. Such an engineering achievement will not only have a transformative impact in soil science and agriculture, but in other fields, including renewable energy, power distribution, and national security. This collaborative research project is co-funded by the Chemical, Bioengineering, Environmental and Transport (CBET) Division in the Engineering Directorate, the Chemistry (CHE) Division in the Directorate for Mathematical and Physical Sciences, the Information and Intelligent Systems (IEE) Division in the Directorate for Computer and Information Science and Engineering, and the Office of Polar Programs. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.