Progress 07/01/19 to 05/31/21

Outputs
Target Audience:The initial target audience for the soil and water nitrate sensors includes certified crop advisors, corn growers association, nutrient research & education council, Iowa Soybean Association that provide consulting services to farmers. These consultants use soil testing to guide nitrogen fertilizer recommendations. There are also many non-certified crop advisors, and certified and non-certified crop advisors service many farms. Revenue from the initial customers will be used to both expand production and invest in broader customer acquisition. This will allow ultimately moving into the broader Digital/Precision Agriculture market as the company grows. Changes/Problems:Initially, we proposed to fabricate the two functional electrodes (working electrode and reference electrode) on a single piece of the wafer substrate. However, this manufacturing cost is very high due to completed fabrication processes and fancy equipment. Therefore, we redesigned the sensor so thatthe working and reference electrodes of the sensor are separated in this new structure. In addition, the reference electrode was redesigned based on a double-junction concept in which two gel-state internal electrolytes were used between the metal contact and the outside testing sample to reduce the depletion of the chloride ion in the inner electrolyte. Compared with the solid-state reference electrode that was proposed, this double-junction gel-state reference electrode greatly improved the sensor's stability and accuracy by providing a more stable reference potential and reducing the signal drift. What opportunities for training and professional development has the project provided?The project provides professional development opportunities to Dr. Wang, the PI of this project to gain increased knowledge in the understanding of ion detection and the development of products. Also, it helps her to increase her skills in accounting, management, and teamwork. In addition, the project provides training opportunities to Fengnan Yang, who graduated from Iowa State University, as a full-time employee. He assisted in the development of nitrate sensors and help to evaluate the nitrate sensors' performance to increase his experimental skills. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Nitrogen fertilizer is one of the greatest input costs to cereal crop production, but the average efficiency of nitrogen fertilizer use is low. Only 30-60% of nitrogen fertilizer is taken up by crops. Large amounts of nitrogen fertilizer are lost to the surrounding environment, representing an economic loss to farmers that is also a significant contributor to water pollution and climate change - nitrous oxide emissions from inefficient N fertilizer use account for more than 5% of total US greenhouse gas emissions. The accomplishment of the proposed project will contribute to the development of highly sensitive sensors that can continuously or instantaneously measure nitrate in soil and water. At a cost of $1-2/measurement, no longer would nitrogen fertilizer application decisions be based on generalized conventional wisdom or a few soil samples that require days of laboratory processing. Therefore, data provided by nitrate sensors can improve farmers' profitability while making significant reductions in US GHG emissions. Objective 1: to improve the quality of mechanical and chemical materials deposited on printed circuit boards of the soil and water sensors. To achieve this objective, the major activities, experiments, results, and key outcomes are following: We studied 5 different types of sealants, including CW2500, 3M6434, 473-1405, EGS10C-20G, and 3M162772to determine the appropriate one that provides a high bonding strength between the epoxy and the device substrate. We examined the waterproof ability of the sensor through optimizing sealant curing conditions. For each sealant, we studied its curing condition, waterproof ability from atmosphere pressure, water absorption rate, and its resistance to deterioration from organisms and substances in soil and tile drainage water. The characterization shows that among all the tested sealants, 3M6434 is the best-performing one due to its low water absorption rate (6.64 mg/hr), rapid curing (7 hrs @ 40°C), and excellent waterproof ability (>30 days). We, therefore, selected 3M6434 to obtain waterproof sealing around the edges of the sensor electrodes. In addition, while continuing our effort to optimize the solid-state reference electrode for the soil and water nitrate sensor, we developed a miniature double-junction reference electrode that outperforms the solid-state reference electrode in terms of sensor lifetime and stability. We used gelatin mixed with KCl and CH3COOLi to replace the liquid-state filling solutions used in conventional large-sized double-junction or single-junction reference electrodes. The fabricated miniature double-junction reference electrode has been demonstrated to provide high stability (76 µV/hr drift rate) in response to different standard nitrogen solutions (KNO3). The accomplishment of this objective helps to improve measurement accuracy and avoid producing nonsense output signals. Objective 2: To realize rapid release of accumulated charges on the working electrode (to test the hypothesis that during ion sensing, the interfacial charges could accumulate at the ion-to-electron transfer layer to influence sensor accuracy). To achieve this objectivewe designed two discharging methods to release all possible accumulated charges on the working electrode. The first method relies on manual connecting and disconnecting of the working electrode with the signal ground, while the second method uses a discharging electronic circuit based on a CMOS-based switch. Both the discharging methods show that although the discharging circuit can help to release the charges, it does not contribute to improving the sensor performance. Therefore, we have decided not to use the discharging circuit in the prototyping. Another effort to achieve this objective is an on-sensor Faraday shield to minimize possible space charge effects and electromagnetic interference. We designed a simple shield made of aluminum foil to encompass the testing samples container so that the whole testing device including the sensor and the testing samples were surrounded by the shield. The slope and R-square values for the linearity fitting between the standard solutions values and the reading values indicated that the Faraday shield did not contribute to improving the sensor performance either. Therefore, we have decided not to use it in the prototyping as well. Object 3: To realize the antifouling of the sensor for long-term measurements. To avoid the fouling effect on the sensor, we used four mesh screens with a mesh size of 10, 20, 30, and 40 to wrap up the sensor to minimize or prevent the settlement of fouling organisms and left them in title water and soil. After 45 days, we used the sensor to randomly test 5, 10, 25,50, and 100 ppm of NO3-N standard solutions. The result showed a 40-size copper mesh and without copper, the mesh had less fouling on the sensor's face compared with other mesh sizes copper. Therefore, we decided not to use the mesh since it did not obviously affect the sensor's long-term performance. Objective 4: To test the prototype sensors for the detection of nitrate in soil and water samples. To test the accuracy of the nitrogen sensor, we set five standard solutions which were prepared by dissolving potassium nitrate (KNO3) into DI water to make 5, 10, 25, 50, and 100 ppm NO3-N and we tested 10 measurements for each solution. We achieved the biggest absolute value of accuracy for the range from 5 to 100 ppm is 3.8, which also means the worst case for the full range, thus, the result meets our specification in Phase I. Besides, we left the sensor in a 50 °C environment for one hour and then were used to measure the standard solutions to test the effect of temperature on the nitrogen sensor. The result is quite close to room temperature. Also, we did a series of experiments to see the chloride ion interference, the biggest interfering ion in the water. We added 0 ppm, 5 ppm, 10 ppm, 25 ppm, 50 ppm, and 100 ppm Chloride ion into six groups of standard solution same with above. We got the correlation coefficients for each group, and the results showed the chloride ion did not affect the accuracy of the sensor. Finally, we validated the prototyping with soil and tile water samples obtained from local cornfields by comparing sensor output with conventional spectrophotometer nitrogen measurement. For the sensor measurement method, three rounds of reading were conducted for each sample, and the average value was obtained to calculate the accuracy. If we consider the spectrophotometer readings are the real values, the accuracy of the sensor is within ±5 ppm. Besides instantaneous measurement, our sensing system can be left in the field for continuous measurement. To validate this, we left the system outside and used the standard solution to substitute the tile water for 45 days, and the sampling rate is once a day.By testing standard solutions, our developed nitrogen sensing system is proven to be accurate between 1-100 ppm in vitro and in vivo produces agronomically relevant measurements of nitrate concentrations in soil and tile water. Also, it can be confirmed that the sensor could not only be able to conduct serial instantaneous testing of approximately 5 minutes/sample, but also could conduct long-term continuous monitoring for at least 45 days. In summary, we have accomplished the proposed objectives. The achievement of these objectives helps us to move a key step forward towards making the nitrate sensors commercially viable. The project made it possible to test the hypotheses that affect the sensor performance and are obstacles to investment in the development of nitrate sensors, including the selection and use of sealing materials, the discharging of accumulated charges from sensitive materials, and the resistance to biofouling. The ability of instantaneous and continuous monitoring has been improved, and the sensor accuracy has been within ±5%.

Publications

Progress 07/01/20 to 02/28/21

Outputs
Target Audience:We met Dr. Jim Friedericks from Agronomy Support. He is very interested in our Nitrate sensors and wants to explore a way to use the sensors in their lab setting that would address their need to quickly process soil samples. Changes/Problems:The major changes/problems encountered during the reporting period are described as followed: 1)Wireless Bluetooth communication between the circuit and the cellphone consumed too much power. An LCD display was added to directly show the measurement results. The cellphone reading became optional for users to reduce power consumption in the field experiments. 2)The gelation used in the reference electrode failed to survive if the temperature is higher than 35°C. Another type of material, agar, was used to replace the gelation to make gel state analyte. 3)PE frit with 30 mm porosity failed to prevent the evaporation of agar in the reference electrode. A metal frit with 50 nm porosity with a higher cost and better performance was selected. But the higher cost of the reference electrode is not a part of the replaceable components. 4)Regular fan could not provide enough wind to dry the sensor's surface. An air blower with high power was used and a 3D printed tube was designed to provide a smooth air pathway. Since the air blower needs 12 V, 1.4 A power to drive, a big battery with 12 V and 7.4 A was used. 5)For long-term measurement applications, the system might be damaged by the rain. So a plastic storage box was used to enclose the system, only the waterproof solar panel, the sampling, and wasting water tubing were left outside. What opportunities for training and professional development has the project provided? The project provides professional development opportunities to Dr. Wang, the PI of this project to gain increased knowledge in the understanding of ion detection and the development of products. Also, it helps her to increase skills in accounting, management, and teamwork. In addition, the project provides training opportunities to Fengnan Yang, who graduated from Iowa State University', as a full-time employee. He assisted in the development of nitrate sensors and help toevaluatethe nitrate sensors' performance to increase hisexperimental skills. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?We are going to accomplish objective 4 during the next reporting period. The specific actions are as followed: 1)Develop experimental protocols for testing soil and tile water samples from local cornfields. 2)Test the sensing system to continuously monitor the tile water/soilfor the long-term (one month).

Impacts
What was accomplished under these goals? Nitrogen fertilizer is one of the greatest input costs to cereal crop production, but the average efficiency of nitrogen fertilizer use is low. Only 30-60% of nitrogen fertilizer is taken up by crops. Large amounts of nitrogen fertilizer are lost to the surrounding environment, representing an economic loss to farmers and diminishing air and water quality. The accomplishment of the proposed project will contribute to the development of highly sensitive sensors that can continuously or instantaneously measure nitrate in soil and water. At a cost of $1-2/measurement, no longer would nitrogen fertilizer application decisions be based on generalized conventional wisdom or a few soil samples that require days of laboratory processing. Therefore, data provided by the nitrate sensors can improve farmers' profitability and reduce the environmental impact of farms across the globe. We have accomplished objects 1 and 2 during the last reporting period. In this reporting period, we accomplished object 3 and part of object 4. Object 3: To realize the antifouling of the sensor for long term measurements. To avoid the fouling effect on the sensor, we used four mech screens with a mesh sizeof 10, 20, 30, and 40 to wrap up the sensor to minimize or prevent the settlement of fouling organisms and left them in title water and soil. After 45 days, we used the sensor to randomly test 5, 10, 25,50, and 100 ppm of NO3-N standard solutions. The result showed 40-size of cooper mech and without copper mech had less fouling on the sensor's face compared with other mesh sizes copper. Therefore, we decided not to use the mesh since it did not obviously affect the sensor's long term performance. Objective 4: To test the prototype sensors for the detection of nitrate in soil and water samples. To testthe accuracy of the nitrogen sensor, we set five standard solutions which were prepared by dissolving potassium nitrate (KNO3) into DI water to make 5, 10, 25, 50, and 100 ppm NO3-N and we tested 10 measurements for each solution. We achieved the biggest absolute value of accuracy for the range from 5 to 100 ppm is 3.8, which also means the worst case for the full range, thus, the result meets our specification in Phase I. Besides, in order to test the effect of temperature on the nitrogen sensor, we left the sensor in a 50 °C environment for one hour and then was used to measure the standard solutions, which are 5, 10, 25, 50, and 100 ppm. The result is quite close to room temperature. Also, we did a series of experiments to see if the chloride ion has an effect on the sensor's measurement, due to the biggest interfering ion is chloride in the water. We added 0 ppm Chloride ion, 5 ppm Chloride ion, 10 ppm Chloride ion, 25 ppm Chloride ion, 50 ppm Chloride ion, and 100 ppm Chloride ion into six groups of standard solution same with above. We got the correlation coefficients of each group test result and showed the chloride ion did not affect the accuracy of the sensor. We also want to test the prototype sensors with soil and tile water samples obtained from local cornfields, which will be accomplished later.

Publications

Progress 07/01/19 to 06/30/20

Outputs
Target Audience:We met Dr. David Brown (Email: david@pivotbio.com) of Pivot Bio discussing the potential collaborations between EnGeniousAg and Pivot Bio on September 3rd in Ames, Iowa. Pivot Bio is interested in testing our nitrogen sensors to test the efficiency of nitrogen-producing microbes as a crop nutrition tool for farmers. Changes/Problems:Based on the results from Objective #1 (see above), we now plan to move forward with evaluating a sensor prototyping employing a double junction reference electrode in parallel with our original plan for a solid-state reference electrode based sensor. What opportunities for training and professional development has the project provided?The project provides trainingopportunities to two of Iowa State University'sundergraduate students, Ally Lorber and Tina Dang, as part-time employees. The two employees assist in the nitrate sensor's evaluation to learn the nitrate measurement process and to increase their experimental skills. In addition, the project provides professional developmentopportunities to Dr. Wang, the PI of this project to gain increased knowledge in the understanding of ion detection and sensor's development. Also, it helps her to increase skills inaccounting andmanagement. How have the results been disseminated to communities of interest?The company gave a product demo at the ARPA-e energy innovation summit, July 8-10, 2019, in Denver, Colorado. The Summit is an annual conference and technology showcase that brings experts from different technical disciplines and professional communities to think about America's energy challenges in new and innovative ways. Our demo attracted >50 people during the Summit. What do you plan to do during the next reporting period to accomplish the goals?We plan to achieve Objective 3 (studying the antifouling of the sensor for long term measurements) and Objective 4 (testing prototype sensors for detection of nitrate in soil and water samples). The specific actions are following: (1) Implement antifouling methods on the prototype sensors. (2) Develop experimental protocols for testing real soil and water samples. (3) Evaluate the sensor prototypes using the samples collected from fields. (4) Design outlook of sensor prototype.

Impacts
What was accomplished under these goals? Nitrogen fertilizer is one of the greatest input costs to cereal crop production, but the average efficiency of nitrogen fertilizer use is low. Only 30-60% of nitrogen fertilizer is taken up by crops. Large amounts of nitrogen fertilizer are lost to the surrounding environment, representing an economic loss to farmers and diminishing air and water quality. The accomplishment of the proposed project will contribute to the development of highly sensitive sensors that can continuously or instantaneously measure nitrate in soil and water. At a cost of $1-2/measurement, no longer would nitrogen fertilizer application decisions be based on generalized conventional wisdom or a few soil samples that require days of laboratory processing. Therefore, data provided by the nitrate sensors can improve farmers' profitability and reduce the environmental impact of farms across the globe. Objective 1: to improve the quality of mechanical and chemical materials deposited on printed circuit boards of the soil and water sensors. To achieve this objective, the major activities, experiments, results, and key outcomes are following: We studied 5 different types of sealants, including CW2500, 3M6434, 473-1405, EGS10C-20G and 3M162772 (all purchased from DigiKey Inc.), to determine the appropriate one that provides a high bonding strength between the epoxy and the device substrate. We examined the waterproof ability of the sensor through optimizing sealant curing conditions. For each sealant, we studied its curing condition, waterproof ability from atmosphere pressure, water absorption rate, and its resistance to deterioration from organisms and substances in soil and tile drainage water (ongoing). The characterization shows that among all the tested sealants, 3M6434 is the best-performing one due to its low water absorption rate (6.64 mg/hr), rapid curing (7 hrs @ 40°C), and excellent waterproof ability (>30 days). We, therefore, selected 3M6434 to obtain waterproof sealing around the edges of the sensor electrodes. In addition, while continuing our effort to optimize the solid-state reference electrode for the soil and water nitrate sensor, we developed a miniature double-junction reference electrode that outperforms the solid-state reference electrode in terms of sensor lifetime and stability. We used gelatin mixed with KCl and CH3COOLi to replace the liquid-state filling solutions used in conventional large-sized double-junction or single-junction reference electrodes. The fabricated miniature double-junction reference electrode has demonstrated to provide high stability (76 µV/hr drift rate) in response to different standard nitrogen solutions (KNO3). The accomplishment of this objective helps to improve measurement accuracy and avoid producing nonsense output signals. Objective 2: To realize rapid release of accumulated charges on the working electrode (to test the hypothesis that during ion sensing, the interfacial charges could accumulate at the ion-to-electron transfer layer to influence sensor accuracy). To achieve this objective, the major activities, experiments, results, and key outcomes are following: We designed two discharging methods to release all possible accumulated charges on the working electrode. The first method relies on manual connecting and disconnecting of the working electrode with the signal ground, while the second method uses a discharging electronic circuit based on a CMOS-based switch. Both the discharging methods show that although the discharging circuit can help to release the charges, it does not contribute to improving the sensor performance. Therefore, we have decided not to use the discharging circuit in the proposed sensor. Another ongoing effort to achieve this objective includes the design of an on-sensor Faraday shield to minimize possible space charge effects and electromagnetic interference. We plan to report the result in the next report. Objective 3: To realize the antifouling of the sensor for long term measurements (ongoing). Objective 4: To test prototype sensors for the detection of nitrate in soil and water samples (ongoing). We made five soil/water prototype sensors. These prototypes were tested using standard nitrate solutions from 0 to 500 ppm. We are testing the sensor using soil and tile water samples obtained from local cornfields.

Publications

Progress 07/01/19 to 02/29/20

Outputs
Target Audience:We met Dr. David Brown (Email: david@pivotbio.com) of Pivot Bio discussing the potential collaborations between EnGeniousAg and Pivot Bio on September 3rd in Ames, Iowa. Pivot Bio is interested in testing our nitrogen sensors to test the efficiency of nitrogen-producing microbes as a crop nutrition tool for farmers. Changes/Problems:Based on the results from Objective #1 (see above), we now plan to move forward with evaluating a sensor prototyping employing a double junction reference electrode in parallel with our original plan for a solid-state reference electrode based sensor. What opportunities for training and professional development has the project provided?The project provides trainingopportunities to two of Iowa State University'sundergraduate students, Ally Lorber and Tina Dang, as part-time employees. The two employees assist in the nitrate sensor's evaluation to learn the nitrate measurement process and to increase their experimental skills. In addition, the project provides professional developmentopportunities to Dr. Wang, the PI of this project to gain increased knowledge in the understanding of ion detection and sensor's development. Also, it helps her to increase skills inaccounting andmanagement. How have the results been disseminated to communities of interest?The company gave a product demo at the ARPA-e energy innovation summit, July 8-10, 2019, in Denver, Colorado. The Summit is an annual conference and technology showcase that brings experts from different technical disciplines and professional communities to think about America's energy challenges in new and innovative ways. Our demo attracted >50 people during the Summit. What do you plan to do during the next reporting period to accomplish the goals?We plan to achieve Objective 3 (studying the antifouling of the sensor for long term measurements) and Objective 4 (testing prototype sensors for detection of nitrate in soil and water samples). The specific actions are following: (1) Implement antifouling methods on the prototype sensors. (2) Develop experimental protocols for testing real soil and water samples. (3) Evaluate the sensor prototypes using the samples collected from fields. (4) Design outlook of sensor prototype.

Impacts
What was accomplished under these goals? Nitrogen fertilizer is one of the greatest input costs to cereal crop production, but the average efficiency of nitrogen fertilizer use is low. Only 30-60% of nitrogen fertilizer is taken up by crops. Large amounts of nitrogen fertilizer are lost to the surrounding environment, representing an economic loss to farmers and diminishing air and water quality. The accomplishment of the proposed project will contribute to the development of highly sensitive sensors that can continuously or instantaneously measure nitrate in soil and water. At a cost of $1-2/measurement, no longer would nitrogen fertilizer application decisions be based on generalized conventional wisdom or a few soil samples that require days of laboratory processing. Therefore, data provided by the nitrate sensors can improve farmers' profitability and reduce the environmental impact of farms across the globe. Objective 1: to improve the quality of mechanical and chemical materials deposited on printed circuit boards of the soil and water sensors. To achieve this objective, the major activities, experiments, results, and key outcomes are following: We studied 5 different types of sealants, including CW2500, 3M6434, 473-1405, EGS10C-20G and 3M162772 (all purchased from DigiKey Inc.), to determine the appropriate one that provides a high bonding strength between the epoxy and the device substrate. We examined the waterproof ability of the sensor through optimizing sealant curing conditions. For each sealant, we studied its curing condition, waterproof ability from atmosphere pressure, water absorption rate, and its resistance to deterioration from organisms and substances in soil and tile drainage water (ongoing). The characterization shows that among all the tested sealants, 3M6434 is the best-performing one due to its low water absorption rate (6.64 mg/hr), rapid curing (7 hrs @ 40°C), and excellent waterproof ability (>30 days). We, therefore, selected 3M6434 to obtain waterproof sealing around the edges of the sensor electrodes. In addition, while continuing our effort to optimize the solid-state reference electrode for the soil and water nitrate sensor, we developed a miniature double-junction reference electrode that outperforms the solid-state reference electrode in terms of sensor lifetime and stability. We used gelatin mixed with KCl and CH3COOLi to replace the liquid-state filling solutions used in conventional large-sized double-junction or single-junction reference electrodes. The fabricated miniature double-junction reference electrode has demonstrated to provide high stability (76 µV/hr drift rate) in response to different standard nitrogen solutions (KNO3). The accomplishment of this objective helps to improve measurement accuracy and avoid producing nonsense output signals. Objective 2: To realize rapid release of accumulated charges on the working electrode (to test the hypothesis that during ion sensing, the interfacial charges could accumulate at the ion-to-electron transfer layer to influence sensor accuracy). To achieve this objective, the major activities, experiments, results, and key outcomes are following: We designed two discharging methods to release all possible accumulated charges on the working electrode. The first method relies on manual connecting and disconnecting of the working electrode with the signal ground, while the second method uses a discharging electronic circuit based on a CMOS-based switch. Both the discharging methods show that although the discharging circuit can help to release the charges, it does not contribute to improving the sensor performance. Therefore, we have decided not to use the discharging circuit in the proposed sensor. Another ongoing effort to achieve this objective includes the design of an on-sensor Faraday shield to minimize possible space charge effects and electromagnetic interference. We plan to report the result in the next report. Objective 3: To realize the antifouling of the sensor for long term measurements (ongoing). Objective 4: To test prototype sensors for the detection of nitrate in soil and water samples (ongoing). We made five soil/water prototype sensors. These prototypes were tested using standard nitrate solutions from 0 to 500 ppm. We are testing the sensor using soil and tile water samples obtained from local cornfields.

Publications