Progress 05/15/07 to 01/14/09
Outputs
OUTPUTS: YSI, Inc. successfully developed and deployed a microfluidics-based nutrient analyzer capable of determining the concentration of soluble reactive phosphate in environmental waters. Two separate analyzers were deployed and logged data for extended periods of time, one of which was battery powered and deployed at the Ohio State University wetlands. Each of the analyzers was deployed for a period of several months from May to September with periodic reagent regeneration and data downloads. The analyzer consisted of 5 subsystems: sample introduction, colorimetry reagents in sealed reservoirs, microfluidic-based fluid handling network, small volume liquid-core waveguide optical detector, and data acquisition and control electronics. All subsystems were housed in an enclosure to provide protection from the elements during deployment. Project efforts focused on developing the subsystems that comprised the analyzer. Some of the technologies used were commercially available and only had to be adapted for use with the analyzer while others were developed and fabricated in-house. Each subsystem was characterized individually and in the integrated analyzer. Following laboratory testing, an analyzer was deployed at a wetland on the Ohio State University campus. Several challenges were initially met during the deployment such as wetland supply pump failure which resulted in the drying out of the wetland. The overall deployment at the Ohio State University site lasted 3 months. Additionally, a second system was deployed at the public water intake and treatment utility in Columbus, Ohio. This site provided environmental protection, temperature stability, and AC power which afforded a much longer deployment time. This Phase I SBIR established that a complex microfluidic-based phosphate analyzer can be developed and deployed for long term environmental monitoring. Although there are challenges in deploying such a complicated system, most of them have been identified and a reasonable solution can be implemented. Additionally this technology, demonstrated for phosphate, forms the basis for a deployable monitoring system of all four of the major detrimental nutrients seen in environmental waters. PARTICIPANTS: YSI, Inc. recognizes all who aided in the development and the achievements of this project: Dr. Mike Dziewatkoski, Scientist, YSI, Inc. Dr. Kevin Schlueter, Bio-Chem Scientist, YSI,Inc. Dr. Joe Dong, Optics Engineer, YSI, Inc. Dr. Melanie Poon, Scientist, YSI, Inc. Dr. Xiaoshan Zhu, Scientist, YSI, Inc. Mr. Matt Smith, Electrical Engineer, YSI, Inc. Mr. Justin Bir, Mechanical Engineer, YSI, Inc. Mr. Chris Palassis, Optics Engineer, YSI, Inc. Mr. Don Moles, Microfluidics Engineer, Micro Molar Systems, LLC. Mr. Larry Whalen, Machinist, YSI, Inc. Wilma H. Schiermier Olentangy River Wetland Research Park at the Ohio State University for providing a protected deployment site The city of Columbus, Ohio's Dublin Road Utilities Complex for providing a protected deployment site TARGET AUDIENCES: The target audience for this effort includes environmental professionals, scientists, engineers, and administrators interested in monitoring nutrient levels in environmental waters. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Over the course of this SBIR Phase I contract we have learned that the microfluidic nutrient analyzer can make accurate phosphate measurements in a laboratory setting with good precision and stability and can also be deployed in the field. The detection limit under ideal conditions is approximately 1 part per billion. However, it was found that changes in ambient temperature do affect the precision of the system. Additionally, the system deployed at the wetland exposed system level functionality challenges that have been mitigated, such as pneumatic leaks. The analyzer can make measurements on approximately 20 microliters of reaction mixture (reagents plus sample or standard) that is analyzed in a 12 microliter optical absorbance detector. We have also learned that one-month-aged ascorbic acid does not affect system performance which is important for extended deployments. Additionally, the effects of biofouling on the sample introduction sub-system have been characterized and a successful flush procedure has been developed. The effects of bubbles propagating in the analyzer can be greatly diminished by careful optical detector geometry and cleaning procedures. Finally, the analyzer was successfully deployed at multiple sites which established the feasibility of developing a microfluidic-based nutrient analyzer which forms the basic building block of a multiple nutrient analyzer.
Publications
- No publications reported this period
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Progress 05/15/07 to 05/14/08
Outputs
This Phase I study is limited to demonstrating the feasibility of using a microfluidic-based analyzer for the colorimetric analysis of orthophosphate in environmental waters. There are 6 project goals. The first four pertain to sub-system design and development (optical detector, chemical reagents, microfluidic reactor, sampling interface), the fifth is to integrate the four sub-systems in to an analyzer, and the sixth is to deploy the analyzer in the field. Five laboratory-based analyzer systems were assembled and tested. Each system consisted of a microvolume absorbance detector, a microfluidic-based liquid handling network to perform the colorimetric chemical reaction, chemical solutions adapted to the orthophosphate analysis in the microfluidic, and a sample introduction device that included a filtration mechanism. One of the lab systems was adapted for field deployment by placing it in an enclosure containing a reagent reservoir, battery, and small compressed gas
cylinder. It was deployed at Ohio State's Wilma H. Schiermier Olentangy River Wetland Research Park at the end of April 2008 and is still currently deployed. The system is programmed to analyze the water at the site one time every hour. This field testing is expected to continue in to June 2008. The remaining four laboratory systems are being used for research and development efforts for producing the next version of the analyzer. Daily deployment-site grab samples of water are being collected for comparative laboratory analysis. The results will allow us to evaluate the performance of the field analyzer.
Impacts
Thus far we have learned that the analyzer can make accurate orthophosphate measurements in a laboratory setting with good precision and stability. The detection limit for the analyzer is below 10ppb P. Changes in ambient temperature do affect the precision of the system and thus we are working to eliminate this effect. The system deployed at the wetland is providing good performance although thus far the phosphate levels at this site appear to be below the detection limit of the instrument. We have learned that the systems can make measurements using as little as 4 microliters of total reagent per analysis and less than 36 microliters of sample (or standard). The analyzer can make measurements on less than 40 microliters of reaction mixture (reagents plus sample or standard). Biofouling of the sample introduction sub-system has not been a problem to this point although it is early in the field deployment and we have yet to learn if this will be a problem later.
Indications to this point are that the sample introduction system is capable of preventing biofouling in the microfluidic reactor. Power management is not optimal at this point. Future work will be directed toward the design and development of more power efficient control and data collection electronics.
Publications
- No publications reported this period
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