SBIR-STTR Award

This Small Business Innovation Research (SBIR) Phase I project will demonstrate proof of concept and validate the feasibility of translating a molecular receptor for nitrate anion into a highly-selective and sensitive soil probe. Ultimately, these sensors will fulfill the need for real-time monitoring of fertilizer application in environmentally sustainable precision agriculture. Both the ion-selective electrode and chemically modified field effect transistor interfaces currently used for nitrate monitoring are capable of measurements only in aqueous media. These sensors rely solely upon non-specific interactions for their selectivity due to a general lack of nitrate selective receptor components. This limitation preempts their use in soil media where highly competitive interferents diminish response. The first innovation proposed herein is the development of a sensor incorporating a rationally designed and intrinsically selective host molecule, which will provide the affinity for nitrate needed to enable monitoring in soils on a molecular level. This technology will then enable a second innovation: a field-embeddable soil sensor network that wirelessly reports fertilizer levels during application in real-time. These innovations will enable molecularly selective sensing in soil, and will pave the way for the development of future molecular sensors for monitoring difficult-to-target anionic and neutral substrates in complex media. The broader impact/commercial potential of this project is the simple need for feeding the world sustainably. Increasing food production capacity by two-fold in the next 30 years, while concurrently decreasing the environmental impact of nonpoint-source pollution has been identified as one of the grand challenges facing the sciences. Nitrate-based fertilizer accounts for almost 60% of the 21M tons of fertilizer applied annually and almost 30% of this is wasted due to seepage, runoff and volatilization. Conserving even 20% of the 2.5M tons of domestic fertilizer that ultimately contribute to nonpoint-source pollution would save growers an average of $45/acre annually, giving rise to an annual market in the U.S. worth approximately $2.1B. Additionally, real-time monitoring of soil macronutrients will enhance understanding of soil chemistry by providing snapshots of the in situ behavior and fate of these chemicals. On a global scale the development of a low-cost and universal probe for soil quality would offer developing areas a novel method for optimizing yields and enabling self-sufficiency in food production. Additionally, these sensors will address the environmental dilemma of groundwater contamination with a foundational solution: limiting the wasteful over-application of fertilizers in food, flower and grain production

The broader impacts/commercial potential of this project both stem from the need to understand the post-application spatial distribution of nitrate below ground. Simply put, the market pull for fertilizer management tools stems from the amount of nitrate fertilizer applied annually (~59% of all applied fertilizer, 12.29M tons domestically), and the estimated waste rate of >30%. This lost input over 442M acres of US farmland results in huge operational expenditures with little to no correlation to yield or profitability increase, and is responsible for the degradation of waterways and groundwater both in the US and abroad. Increasing our food production capacity by two-fold in the next 30 years while concurrently decreasing the environmental impact of agricultural nonpoint-source pollution has been identified as one of the ?Grand Challenges? facing the chemical and engineering sciences. On a global scale the development of a low-cost and universal probe for soil quality would offer developing areas a novel method for optimizing yields and enabling self-sufficiency in food production, regardless of remoteness or laboratory availability. Additionally, a tool for in situ nitrate measurement will offer an important tool for tracking and mapping organic contaminant plumes during groundwater remediation activities.This Small Business Innovation (SBIR) Phase 2 project will enable wafer-level processing and pilot-scale production of chemically modified field effect transistors (CHEMFETs) containing a novel molecular receptor for nitrate anion. These sensitive components will be incorporated into patent-protected modules that achieve direct, in situ measurement of nitrate in soils without sample preprocessing. Current methods for measuring nitrate anion in soil all require on-site or in-lab preprocessing of the samples due to limitations of the ionophore in competitive media, especially in the presence of common chloride anion. Phase I development showed that by incorporating a molecular receptor with high sensitivity and specificity for nitrate, systems comprised of CHEMFETs containing these molecular receptors yield sensors capable of reporting nitrate concentration at single digit parts per million (ppm) resolutions in the presence of >3 orders of magnitude greater chloride concentrations. Phase 2 will develop a wafer-level deposition process that is compatible with the molecular receptor while avoiding incompatible mask/de-mask processes. Ultimately, this development process will prove the manufacturability of these sensors, and provide the foundation for large-scale distributed beta testing by customers and end-users at the completion of Phase 2.